After 1♦  South is probably best to double - opening points and support for the other suits. North should jump to 2♥ s to show 8-11 points as he had passed. East does not have enough distributino to bid 3♦ s.

South has no extras so passes.

In duplicate leaving the opposition to play at the 2 level in a fit is not good so West should probably bid 3♦ s as delayed support.

North has reasonable shape and another ♥ so can bid 3♥ s which will often make.

2♣ strong hand opener.

2♦  as with less than A and K (or relay to allow the strong hand to show hand).

2♥ 5+♥ s

3♥  response is stronger than 4♥ as it allows the strong hand to find the best fit or explore a slam.

3♠ a cue bid (A/K or void/singleton) shows an interest in slam

4♦ cue bid which strengthens Easts KQ♦ s

4NT Keycard Blackwood 

5♣ showing one of 5 keycards with 1430 (some will play 5♦  to show one keycard) 

6♥ missing only one keycard so is reasonable slam.

Does North open 4♦ or 3♦ ?

8 card suit but with the objective to be at most 2 down vulnerable (-500) and 6 losers many will bid 3♦ s 

Either way East will bid ♥ s and then West has a difficult decision on whether to bid ♠ s with a 7 card suit, the reason why pre-empts are so powerful. With J9♥ s many will pass 4♥ s but bid 3♠ s (forcing) over 3♥ s and East will then rebid 4♥ s.

South's double shows support for the other 2 suits and 8+ (just) points.

Over North's 2♠ s some East's may bid 3♥ s and then South has to decide whether to bid 3♠ s or defend, as his hand is quite defensive. 

If in soubt with this vulnerability it is probably correct to bid on.

Classic weak 2♥ opener.

South will normally go via a 2NT enquiry or Ogust.

West could bid 3NT here which is an unusual NT showing 5/5 in the lowest two unbid suits.

North has to decide between showing a strong hand by showing his feature with 3♦ or bidding 3♥ to show a weak hand. 6322 distribution is not great but he has 7 HCPs and some tens and nines.

South will sign off in 4♥ s 6/3 fit with the trumps in the weak hand will probably play better.

5♣ s doubled goes 2 off and would be a top for E/W

The K♣ lead put's pressure on the contract as he will have difficulty in accessing the long ♠ s.

West can make a risky 4NT showing minors bid which works well here. North should pass as he has shown his hand.

East shows his ♣ s .

South has to decide and should probably go to 5♥ s as he has an offensive hand.

South's 2♠ is known as an assuming cue bid, which allows South to show normally a strong raise of partner's suit. If playing this convention it allows South to bid 3♦ s with good diamond support but not a lot of points.

For more information on the Unassuming cue bid

Bidding opposition's suit is often a good bid when you are unsure what to do and seek clarification.

Here North has a reasonable hand and a ♠ stop so if partner has more than minimum he may bid 3NT, but here he is minimum so bids 3♦ .

East has had no support, has a broken ♠ suit and North has at least one stopper in ♠ s so bidding on is probably not a good idea.

East has 3 card support but West has not been able to show his longer suit so probably with this vulnerability East has to pass.

There is a temptation to bid ♥ s with this hand because of the nice 5 card suit and ♦ doubleton. However it is balanced 5332. So after the 1NT response 6-10 HCPs and spades well stopped worth going straight to 3NT.

South has a weak 2♠ opener even with the terrible suit.

North has to grit his teeth and pass.

East with good stops and 21 HCPs should bid 3NT. South has 5-9 points and average of 8 + to his 21 points = 29 so N/W have 11 points so if his partner has his share of this we will be able to make 3N.

Those who play strong 2s will lead to

p-p-p-2N not a great shape but it shows the point count and then West has to decide whether to bid 3♣ stayman which will result in 3N. In his favour is that he has 4HCPs with goodish intermediates. The odds of finding a ♥ fit are about 25%.

Safe 2♦ overcall.

To show a strong raise of ♥ s West could use an unassuming cue bid of 3♦ s. So his bid of 3♥ s shows 4♥ s and is based on the law of total tricks.

East has an extra trump so based on the law of total tricks and a 6 loser hand bids 4♥ s.

When this comes back to North he may consider 5♦ s - risky but it puts pressure on East who must bid 5♥ or double.