Two passes and then a standard 1NT with 12-14 and a balanced hand.

East transfers to ♠ s by bidding 2♥ .

Generally this will play easier and score higher in duplicate than 1NT.

With best play you can make 2 more tricks in ♠ s than NTs.

Interesting hand.

Balanced hand but with 15 points, plan to bid 1♣  and rebid 1NT to show 15-16 HCPs.

South can overcall 1♥ with 5♥ s. For an overcall you can take a King away from a normal opening bid to make the overcall.

Wests double shows 8+points and support for the other suits.

East bids should probably bid 2NT as if West has a bit more you can get to game. 1NT here probably shows a 12-14 point hand with clubs and denying 4♠ s (the priority to show over the double).

West has more than 8 points and can raise to 3NT.

West opens 1♦ , the East response of 2♣ s shows 8+points so West knows they have enough for game.

3♦  shows 16+ HCPs and long ♦ s.

East shows a ♠  stop to look for 3NT which is often the best contract for duplicate.

West bids 3NT which looks a safe game. 

6♦ is a lot riskier opposite a passed hand and should not make from West.

1NT opener.

South doubles with 15-17HCPs

West passes as he knows they have 20+ HCPs

North must do something as he knows 1NT doubled will make.

There are systems like Landy which would help.

But with natural bids, bid your 5 +card suit or in this case bid your lowest suit which will be probably be passed out.

East has to choose between showing his 5♣ s or 4♠ s.

With only  HCPs East may struggle to show his ♠ s if West responds 2♦ s. So in this case he should bid 1♠. If East has 12+ HCPs he can show his 5♣ s first as he will then be able to bid ♠ s later as they will probably be going to game.

West jumps to 3♣ s to show 16+ HCPs.

East knows they have game values but ♣ s or NTs?

A useful tool is 4th suit forcing which is often used to find a stop for NT or clarify the hand distribuition. If West has a  ♦ stop he can bid  3NT. If not he could show 3♠ s if he had them or   3♥ s if he had an additional ♥ . West does not have a good bid. The ♦ stop is only a doubleton and is very risky, but a less risky bid is 3♥ s, lying on the the length, but it is a good suit.

Over the 3NT East will pass. Over 3♥ s East will support the ♣ s and the best contract of 5♣ s is found.

Not an easy hand.

1NT by West.

East will transfer with 2♦  showing ♥ s

South will compete with 2♠ s.

West should pass as he has only 2♥ s

East should then show his other 5 card suit by bidding 3♣ s which can be passed by West, though he may be tempted to bid 3♥ s.

North Preempts with a length of 7 - 3♥ s

East and South will pass.

West has a difficult decision between pass, double, 3NT, 4♦ s and perhaps 4NT.

If North has 7 HCPs (an average for a preempt), added to Wests 17, that leaves 16 HCPs between East and South. If East has the average amount they have 17 + 8HCPs = 25 and enough for game.

If West doubles (terrible shape for a double) East will likely bid ♠ s, then if West bids ♦ s, East may work out that East has 5♦ s and 4♣ s and a strong hand. If he had bid 4NT which is the unusual NT he shows 5/5 in ♦  and ♣s (a lie). 

4♦ s by West is a possible bid and did well tonight.

3NT is a gamble that, but with good ♥  stops worth a try though it is difficult to make.

Standard 1NT opening.

West has to decide between 3♦ s which may lead to a slam in ♦ s or 3NT which is a safer bid and that generally scores well. Which it does in this case.

1♥  by opener.

West can do a weak jump overcall with 6-9 and a 6+ card suit. Risky, but it makes life difficult for North. 

North has 8HCPs so should double, though the shape is not great.

Then South has to decide between 3♥ s and 3♦ s. Difficult the 6 + 0/1/2 ♥ fit may play OK but you may miss a better 4/4♦  fit.

1♦ opening by South.

1♥ response by North

Raised to 2♥ s by South

Norths hand looks good for 9 points. He has Aces rather than Qs (that are overvalued) and a couple of 10s comibined with support for the ♦ s of opener so he can invite game with 3♥ s and south with good shape and a singleton ♠ can bid game.