Presumably you reckoned that declarer has only one heart at most.
Assuming he has one, there is a danger of declarer drawing trumps and then getting spade discards from dummy on his diamonds.
Hence you need to take any spade tricks before he can do this.
So, you need to persuade partner to switch to spades at trick two.
So, did you play the 2♥ , 10♥ or what?

Well, did you realise that you could put partner out of any misery by playing the A♥ at trick 1?
Partner really must have the Q♥ for his lead.  Even if he hasn't, declarer will have it as a singleton.  Are you worried you might set up dummy's Jack?  Well, you shouldn't be parsimonious here as declarer wouldn't get a worthwhile discard.
So, you take your A♥ , cash the A♠ and if partner encourages, continue with a small spade.  If he discourages, switch to a diamond.
The contract is now one off.
If you don't take your A♥ at trick one, partner will almost certainly continue with another heart as he won't like to lead away from his K♠ .  After all, how is he to quess you've got the A♠ and not the A♦ ? 

First, what actually happened.
At trick two declarer finessed the J♦ and N smoothly played low.
He now led a club to his Q and N followed low.
He now took another diamond finesse and was somewhat surprised when N's Queen won.
N led a heart and now the hand collapsed. Declarer played the Ace, tried the Q♠ which N had enough sense to duck.  Another spade and when the dust had settled the contract was minus 4.

N, me, was rather pleased with himself until he looked at the hand printout and saw that if he'd simply taken his Q♦ at trick 2 and led either a club or a heart, the contract was doomed to fail.  I'd actually given declarer the chance to make his contract if he'd now simply cashed the A&K♦ .  He would have made five diamonds, two clubs, one heart and one spade.
If you'd have been declarer and your first diamond finesse had won, how would you have continued??

Now for the analysis.
1. Partner has almost certainly led his 4th highest club.  It's highly likely he's got five.
2. Using the rule of eleven shows that declarer started with three clubs higher than the five.  You already know one of them is the King and you can work out that one of the other two must be the 9 or the 10. Why? Because partner would have led the 10 if he had both the 10 and the 9 - top of an interior sequence.  Hence declarer holds either A&K or K&Q♣ .
3. Declarer is virtually certain to have the Q♠ to justify is 2NT bid.
4. Declarer's distribution is likely to be either 3-4-3-3 or 3-5-2-3.
5. Declarer has a maximum of 14 pts. He's either got 7 or 8 in the black suits and the rest must therefore be in hearts. This means he cannot run the hearts as his maximum holding can only be AK or AQJ.

If I'd actually done what I've just preached I could have worked out that I should have taken my Q♦ and led a club.
I leave you decide if I was clever or too clever by half.
Also, if you were declarer, would you have cashed your AK♦ if your J♦ had held?

You should be regretting your double as you really don't want more spade leads unless partner has KQJ of them. 
Do you particularly want a diamond or a club or do think it's best to let partner to decide how to defend?

If partner has the K♦ you want a diamond lead.  If he has K♣ you want a club lead.  Short of having spectacles which enable you to see through the back of the cards, how do you decide?  Perhaps it's best to put your trust in partner.
But, wait a minute.  The danger is that partner will win the trump trick and cash his Q♠ thus setting up declarer's J♠ for a discard.  A discard of a diamond is unlikely to be of much use to declarer. but a discard of a club could make all the difference between making 4♥ and going one off.  Hence you must do everything you possibly can to encourage partner to lead a club immediately after winning his trump trick.
So, playing natural discards, you're best bet is to discard the Q♣ .
For odds and evens, I suppose you have to discard the Q♣ .  Personally, I detest this discarding system.  Will partner read this as an even card?  What would I have discarded if my clubs had been Q9753 ?
For Mckenney, the 5♠ (or the 4♠ depending on which card you played to trick 1) looks best.  Whether partner will read this as specifically asking for a club or you simply saying you're not much interested in clubs is open to question.

Now put yourself in East's position immediately after you've won your trump trick and seen W's discard.
If you're playing teams, unless W has specifically encouraged you to continue with spades, I suggest you should lead a club as you should see the danger of a club discard from dummy on declarer's J♠ .
If you're playing pairs, I suggest the best chance would still be to lead a club.  Having doubled with such a poor spade suit, there must be a good chance W has the Q♣ .

S has chosen to lead hearts despite, presumably, having two spades.
As N can have only one point in spades, the Jack, it's reasonable to assume (hope?) he will have 7-9 points rather than 5-7, given that N/S are vulnerable.
These are unlikely to include both the A and Q of hearts as surely S would be unlikely to lead a suit headed by the 10 in preference to spades.
Further it seems reasonable to assume S has at least 6 hearts - probably six.

You have three choices of play, K, J or small and need to consider the following

a) How many tricks would W likely make in 3NT?  You need to try and match/better this.
b) When planning the play, is there a a particular approach to take?  In particular, is there one opponent you'd like to keep off lead?
c) Which play will minimse the potential loss of tricks? (this would be especially important if this were teams)
d) Which play, albeit assuming a plausible layout of the heart suit, would maximise your trick taking chances?

Taking a) first.  On a spade lead you look likely to lose one heart, one diamond and, likely, one club.  It's reasonable to assume the diamond honours are split.  Hence 10 tricks is your target. 
With b) you should try to keep South off lead wherever possible - especially when N has run out of hearts.
Now consider the likelihood of the following three heart distributions and how you would play each of them.

1.  S  AQ1098x    N xx
2.  S Q1098xx     N Ax
3.  S A1098xx     N Qx

If it's no. 1 and you're trying to minimise your potential loss then it doesn't matter what you play to the first trick provided you play to win the second trick (assuming S doesn't cash the A♥ at trick 2)
If it's no. 2 then playing low at tricks 2 & 3 will not not only block the suit but provide you with two heart stops thus enabling you to set up the club suit.
If it's no. 3 then playing low at trick's 2 & 3 will guarantee you one trick in hearts and should be sufficient 

What should become apparent is that playing the Jack is almost certainly wrong.  1 or 3 looks the most likely to warrant S leading hearts.  Hence playing the K♥ looks your best bet.

I strongly suggest you go to this hand on the website and use the "Play it again" feature  (access via the button underneath the hand and above the results).
Try leading the 10♥ and experiment with different plays.  Two very instructive ways to play suits will emerge.
i) Say the play has gone Trick 1: 10, J, Q, 4 ♥ . Trick 2: 2♥ , 6♦ , A♥ ,3♥ .  Trick 3: 9♥ ,K♥ , 3♠ , 10♦ . When you lead clubs from dummy, N plays the King.  This should prompt you to stop and think.  How good a player do you think North is?  A good player will smoothly play the King from K doubleton; a weak player would play low holding Kx.  If you think the K♣ is a singleton you should duck.  If you think it's from a doubleton you should win with the Ace.
ii) Trick 1: 10, K, 2, 4♥ .  Trick 2: 5, K, A, 3♣ .  N's play of the K♣ should prompt you to stop and think- see above.    Note the key play of leading a small diamond from hand.  This caters for a singleton honour with S.  Leading the J or 10 of diamonds cannot gain whatever the distribution; here it loses!  Finally, if you follow through this line of play correctly, you'll end up with eleven tricks for a top!!
Perhaps S should have led a spade after all.  
Well no actually.  Muggins played the Jack at trick one, discarded diamonds on the next two heart leads and then covered N's K♣ with his Ace.  Oh dear!
Finally, go back to i) above and replay tricks 1,2 & 3.  Did you spot on trick 3 that the computer software was telling you to play the K♣ ?  If you did, you probably thought it must be a mistake.  However, think back to consideration b) at the top:  declarer wants to keep S off the lead; N should be looking to get S on lead wherever possible. N should realise his singleton K ♣ is useless; and if S has four clubs to the ten and if declarer is good enough to let you win with your King.........  An interesting battle between declarer and defender.

Of the seven people who played in 4♥ , four made 9 tricks & three made 10.
Of the two pairs in 5♥ doubled, one made 9 and the other 10.  N's double should guide E into making 10 tricks.

At teams you should look to ensure you only lose 3 tricks: two hearts and one diamond.  Hence you cross to dummy and run the 9♥ .
But at pairs?
Wouldn't you start with the A♥ in case there's a singleton honour and, if both opponents follow cash the K♥ ?
The 5-0 break is a nasty surprise but all is not lost.
Cash the A♦ and then lead the Q♦ .  You must try to set up your diamonds.  You want N to ruff a diamond to shorten his trumps so you don't mind him ruffing your Ace if there's a 5-0 diamond break.

Now, the attention switches to South.  He takes his K♦ and sees N discard.
He can either give his partner a diamond ruff or lead another club.
How should he decide?
He should reason that E must have at least 6 hearts and AQJ10x of diamonds.  There is a strong indication that E's hearts are headed by the AK as he didn't cross to dummy and finesse ie.he doesn't have either AQJ  or AKJ.  Hence N looks highly likely to have either QJxx or, hopefully QJxxx.  In this case, giving N a diamond ruff will mean he will be ruffing with what is effectively a natural trump trick.  Hence S should lead another club.  Try as he might, E has now lost control of the trump suit and will lose 3 trump and one diamnond trick.

S simply couldn't believe N could have 3 "Aces".  I think he would do better to have rebid 2♠ then, when using RKC Blackwood, the response could only show Aces.
After 6♦ S bid 6♠ which was passed out.
Did you, South, bid 7NT?
I think N's bid of 6♦ after having made the positive 2♥ bid must show he has "3 Aces".  However, the Ace of clubs could be missing.

Note that the simple Blackwood convention would make bidding 7NT dead easy.
Only one pair bid a grand slam.  The results were

once          4♠ +3  (not really the hand to open the bidding with 4♠ !)
five times  6♠ +1
twice          6NT+1
once          7♠ =

Unless N/S have a death wish - which one pair on the night must have had, you will likely end up with a poor score if you bid more than 1♠ .

At my table the bidding progressed

  S       W       N        E
 1♦       P      1♥      1♠ 
 2♥       P      3♥       P
 4♥     Dble   P        P
  P

I think E is too strong to bid anything other than 1♠ .  If partner supports spades you can easily catch up.  If he doesn't, as here, you may only be able to make 1♠ , 

The E/W pair who managed to push N/S into 5♥ dbled must count themselves exceedingly fortunate.

Go to hand no. 2.

Well, what did you, East, make of the auction?
S has shown a hand equivalent to at least an opening bid and West hasn't doubled for takeout but has entered the auction at the 3 level when Vul and N/S being Non-Vul.

Now look at all four hands and see the effect of South's 2NT bid.  He realises E/W are virtually certain to have game on and 2NT can't really cost anything as N will only respond at the 3 level.  2NT might confuse the opposition.  
I have to report that it confused me, East.  I wanted to bid 4♥ but was put off by my distribution and the likelihood of only having one winner.

I agree with W's choice of 3♥ rather than doubling as the likely outcome of a double will be 3♠ by N, passes by E & S and now what would W do?

On the day, six pairs played in 4♥ , one played in 3♥ and one in 2♥ . 
                      two pairs played in 3NT.

As in many situations at bridge there's no right answer but application of thought, combined with both partners working together can help.

I suggest the following analysis can help in this and similar situations.
a) E should assume W has
- either a good six card heart suit but with the likelihood of there being one loser in the suit and some decent outside values
- or a good seven card heart suit but with the likelihood of there being one loser in the suit and few outside values
b) E's club holding looks very useful for NT but the doubleton heart???
c) At teams you simply bid 4♥ .  At pairs you could simply do this or, subject to partnership understanding, you could bid 3NT and expect partner to do the following see d below.
d) On hearing 3NT from E, W reasons as follows
- E will assume I have a likely heart loser.  If I haven't I should Pass.  If I've more than one heart loser I bid 4♥ .  If I've likely got one loser then I should consider passing if I have a definite outside entry, otherwise I should bid 4♥ .  On this particular hand, knowing N must have virtually all the outstanding points, I should bid 4♥ .  This bid is also reinforced as I will be on lead and a spade lead will come up to my King rather than through it.

If your system as E/W is such that 2NT would be a forcing bid then this will make it easier to find out that 4♥ will be the better contract. 

Hopefully your plan for trumps was to start by leading small to the Ace.
Situations a) and b) are the same.  You rise with the Ace and lead back towards the Q,J.
In c) you're pleasantly surprised not to have to lose a trick to the King that you take your Ace and lead towards the Q,J.
You've nothing better to do then than draw trumps and hope E has the A♥ .
E hasn't, so you make your 10 tricks, put the result into the computer, see you've got 50% and reach for the next board.

With the help of an international in the West seat, you subsequently realise you've missed a trick (literally).  When the unexpected appearance of the K♠ occurs you should stop and think.
Can you take advantage of this?  Now you re-count trumps and realise W must have 10,9,x,x and so you are still bound to lose one trump trick.  If you can lose this to West then you can prevent a heart lead through your King and hence, after drawing trumps, discard a heart on the long club and thus make eleven tricks for a top!

We're always told to take our time before playing to the first trick.  The same adage applies during the play if something unexpected occurs.

Prospects do not look good. N has five spade tricks to take if he can get in and it looks quite likely he'll have at least one of the top two diamond honours.

The only hope appears to be that you can set up 5 club tricks.  You cash the A♣ and see N drop the 10♣ .  Hope glimmers more brightly.  You cash the K♣ and can hardly believe your luck when N drops the Q♣ !
BUT, did you plan ahead and drop the J & 9♣ under your Ace and King?  If not, you're now trapped in hand by the J♣ .
If you spotted this then I think you deserved your luck.
If you didn't then you're resigned to cashing the J♣ and have nothing better to do than cash the A& K ♥ .
You now encounter almost unbelievable luck when N drops the Q♥ under the King!
So, you finesse the 9♥ , run your clubs, cash the J♥ and exit with a diamond.
Just to add insult to injury all S can do is to take his A & K♦ and give you the final trick with a diamond.
Would you believe it? 1NT + 4 !

What did you make of partner's 10♥ ?
Was he encouraging you to continue, showing an even number of hearts or what?
Given your view of dummy and remembering the bidding, I suggest both you and your partner should look at the trick taking potential of dummy and realise that attitude and count are irrelevant and that North's play to the first trick should be a Mckenney signal.
For South's bid of 1♠ he won't have many points.  He must have the Q♥ and is unlikely to have both the K♠ and the K♦ .
Hence you should cash the A♠ at trick 2.  If partner encourages, you lead another spade which partner wins, returns a heart and the contract is one off.  A top!
If however you lead the J♥ at trick two, hoping to knock out declarer's Q♥ and then get in with the A♠ , the contract will make with an overtrick and you'll get a bottom.

If you, South, try Blackwood, you'll discover North has two Aces.

On the day, no one reached 6♦ .
Four reached 6♣, two of whom were doubled , three reached 5♣, one of whom was doubled , one tried 6♠  - quite how they got there I really don't know  -, two reached 4♠  and one languished in 3♠ 

How did you do?

1. 1NT was not a success as the bidding went 1NT-P-P-2S.
Everywhere else the bidding went 1H-P-1NT-P-P-P.

2S is an agressive bid to say the least, but with so many points in a five card major I think 1H is a better opening bid.

2. Here 1NT by E worked a treat as it caught the opponents out. S had a balanced opening 1NT and so had to pass, N held

10 7 6 4 2

Q J 6

Q

K J 7 4

and, not unreasonably in my opinion (especially as I was N) N elected to pass.  N/S therefore missed their 2S contract.
Only one East opened the bidding.

3.  As it turned out, pass proved the best result.  Partner had 

8 7 3

Q J 10 3

A J 7

A 7 3

so those who opened 1NT ended up too high, either 2NT or 3H.
Ah well, you win some and you lose some.

4 & 5.  Did you have a different answer for these?
This hand was brought to my attention by the person who found the hand had been sorted.
Do you have unauthorised information?  It looks virtually certain that the hand was passed out at the previous table - and so you mustn't use this information.  So, if you never open 1NT with less than 12 points you may feel you are duty bound to pass.
But what if you have opened 1NT with 11 points on some or even many occasions in the past?  Further, just because you believe the hand to have been passed out before, it doesn't give you a clue as to whether a bid of 1NT by you will give you a top or a bottom.
Finally, you only have about 10 seconds to decide as otherwise a hesitation by you will put partner in a difficult ethical position.
I've asked a few good players about this and there hasn't been a consensus of view.

This situation demonstrates the importance of shuffling your hand after you've played it (even if you haven't played it if you see what I mean)

Please let me know your solution

a) if using a complicated system agreed with your partner
b) if playing a standard version of Acol

Again, please tell me your answer.

How does East find out if E/W have a 5-3 heart fit and then will hearts or NTs score better?
I leave you to look up the results to see what happened.
 

Presumably you decided on a cross-ruff but how well did you look ahead?
From the lead you deduce  N definitely hasn't got the A,K♠ but most probably has the King as he didn't lead the suit.  He doesn't have a solid diamond suit so he most likely has six of them but could he have seven?  If he has seven you need to draw trumps so that your K♦ doesn't get ruffed.  As N didn't jump overcall he is unlikely to have seven.
So, draw one round of trumps in case they're splitting.  When you find they don't, cash the K♦ and embark on the cross-ruff.

Have you tried the "Play it again" feature within this website?  If not, I suggest you try it on this hand.
You'll need to go to the results section and select that for Monday evening 4 January 2015 and locate hand 7. Just below the hand layout click on the button "Play it again"  In the window that appears click on the button "BS Online".  If the makeable contracts isn't showing, click on the button "Analyse".
Click on the contract you wish to play if it isn't already highlighted in yellow.
Now you can play the hand. Start by clicking on the 7♦ and you should rapidly work out how to re-play the hand.

As you play it through you you will come to a stage where you lead your last diamond, probably trick 8, N covers and you should discard your losing spade from dummy.  If you don't, you will find you have to lead a spade at trick10, S will win and lead his last trump.  You can still salvage the contract as long as you remembered to use your A♣ earlier in the play. Now you can make the Q♥ for your 12th trick.

Finally, what would you have led as North?  I'd be inclined to lead the unbid major against a slam even though I only have the King.

Eleven tricks are certain. Five spades, three clubs one diamond and two club ruffs.
What are the options for making 12 or even 13 tricks?

If the clubs break 3-3 or the J♣ falls in three rounds then you have 13 tricks.
I assume you considered the club finesse but rapidly rejected it.
You should only take the diamond finesse when all other avenues have failed.

By now, you should be thinking of maximising your chances of making 12 tricks.
The chances of clubs breaking 3-3 are less than 50%.  If N has 4 or more clubs then you can expect him to lead a diamond, forcing you to take the finesse.
If however, S wins the J ♣ he will be end-played if he holds the A♥ .
If S holds five or six clubs then you only have three club tricks.
Hence the "safety play" to maximise your chances of making twelve tricks is to lead a club to the nine at trick 3. (ie. after having drawn trumps)

Two readers have written to me to say the best line is to cash the A,K of clubs and, on finding the bad break, exit with a small club.  The rest of my analysis holds good.
One of these readers was so engrossed in the hand that he spent that I deduce he spent a good part of a dull morning doing a detaied calculation of the odds.

I trust you decided you wanted partner to switch to a diamond.
So did you follow low and hope partner would find the switch or did you play the Q♠ and hope/expect him to read this as a suit prefernce signal?​

You can work out that declarer only has one spade so he can only make the K♠ at some stage.  However, you must make two diamond tricks before he can discard a diamond.

So, did you employ the standard "rule" of returning your lowest spade ie. 4th highest of your original holding, so as to give partner the count?
If you did then you've made life very difficult for partner.  He will win the Ace and then have to decide if/how to continue spades.  He will have to decide if you started with four or two spades (seeing declarer's 7♠  will mean he can work out you didn't start with three.
He will be a bold man if he underleads his J♠ .

Now, let's go back to trick 2 and assess W & N's spade holding.  W has led 4th highest, given S's play of the 3, W must have either four or five spades.  Hence declarer has only three or two.  You should see the danger of blocking the spade suit and that it can't cost to lead the 10♠ at trick two.  The contract will now go one off.

By blocking the spade suit you give declarer a chance to make his contract.  The defence take their four spade tricks and then give declarer the lead. Superficially he still only has eight tricks.  However, he cashes his heart and three diamond winners to leave the following position

                                               N
                                         ♠ 
                                         ♥ 
                                         ♦ 4
                                         ♣ K64
        W                                                                      E
♠   4                                                               ♠ 
♥   7                                                                ♥ Q
♦                                                                    ♦ 
♣   Q3                                                            ♣ J109
                                            S
                                          ♠ 
                                          ♥ J
                                          ♦ J
                                          ♣ A8

The lead of the J♦ squeezes East.  Lucky for declarer?  Maybe;  but you had your chance to defeat the contract.

Firstly, did you try to assess the likely disttributions for N & S?
S sounds quite strong, at least 5-4 in spades and diamonds and quite likely 5-5.  S is unlikely to have a 6 card suit as she's content to leave 3NT.
N has 5 hearts by bidding 2♥ . He doesn't have 6 or he would have re-bid 3♥ . He will also have a maximium of 2 spades.
So, the probabilities are S has 1 or 2 clubs and N has 4 or 5.  This suggests partner is highly likely to have 4 clubs, possibly 5.

Given N's bidding, it will be surprising if he doesn't have the K♣ .  Hence, ideally, you want partner to lead clubs trhough N's King.  However, given your 10 points, partner is only likely to get in once, if at all.  Now, if you lead a small club, declarer will win and you'll have blocked the suit so partner will never be able to make his long club(s).

You therefore decide to play the A♣ (not the Q as you might just drop a singleton K in dummy).  You observe dummy and beam with pleasure as you table the Q♣ at trick 2.  You will end up with 4 tricks.  In fact this would only result in an average as, whilst you beat every other pair who defended 3NT, you would lose out to those who defended against 4♠ and where declarer failed to make it.

You might like to look at the hands and decide how you would plan the play if you were S in 4♠ .

North chose 5♣ and West (me) chose to double.  West was somewhat surprised to find he never made any of his three "winners".

At another table, W opened 1♥ and N bid 3♣ . How W must have regretted bidding 3♥ as, instead of getting a top, he achieved a bottom by doubling N's next bid of 6♣ .

Just to show how personal battles can interfere with results, on the night before, my partner and I had conspired to achieve our lowest ever %age score by a combination of some poor bidding, some poor play and, of course, a huge helping of bad luck.  Hence we had a gentlemen's bet on which of us would do better on the Wednesday afternoon.  He played this hand during the last round.  He looked at the rolling score screen and saw he was just behind me.  He therefore chose to bid 7♣ at his first opportunity.  Try as he might, he couldn't avoid losing one trick to the Q♦ .

Ah well, it's not often I double a contract, watch declarer rattle off an overtrick to add insult to injury, but end up with 40%.

The scores were:

7♣ dbled minus 1
5♣ dbled minus 1  (I leave you to speculate how this could happen as I didn't hear the director being called about a revoke)
5♣ plus 1
5♣ dbled plus 1
6♣ plus 1
6♣ dbled plus 1

On the night, seven out of eleven pairs chose 3♥ .  It might be eight as one N played in 3NT.
As you can see this was not a success.  After a double by S, N should bid 3♣ , S now bids 3♥ .  N should reason that S has five hearts, only two clubs (as he didn't pass 3♣ ) and probably four diamonds.  Hence N now bids 4♦ which concludes the auction.