Hands are from Adventures in Bridge, October 12, 2018.
North: ♠Q76 ♥6 ♦1087653 ♣954
South: ♠AK832 ♥742 ♦— ♣AQ763
Suggested bidding: 1♠ by South; double by West; pass by North (if you had one more spade, you might risk a preemptive 3♠, but vulnerable, bidding 2♠ or 3♠ on that hand is dangerous). 2♥ (0-8 HCP) by East. South should rebid 3♣. Yes, you have only 13 HCP, but you have a 5 loser hand. The fact that the opponents have almost certainly found a fit makes it more likely your side could have a fit.
Plus, many people play equal-level-conversion doubles. That means that West does NOT guarantee clubs. West could have four hearts and five or six diamonds. So, it is worth showing your second suit. Bidding also serves the purpose of making West's likely 3♥ raise more ambiguous. Does he truly have game invitational values, or is he just competing with a good 15 or 16 HCP?
Over the expected 3♥, North can now bid 3♠, having already warned partner of very limited values. If your side buys it for 3♠, you will be down one—losing two club tricks and three heart tricks IF they put a trump on the table at every opportunity to keep you from a ruff in Dummy. The most likely leads, either a diamond or a heart, both from AKxx, however, give you the time to score TWO heart ruffs in Dummy. You might even make the contract, doubled.
If E/W compete to 4♥, you can choose to defend, hoping to get a diamond ruff. You lead the ♠A (promising the ♠K) and partner plays the ♠7 to encourage. Although the spots are scary, you have to trust that partner has played ♠7 from ♠Q76 and Declarer's ♠9 is from ♠J109. You play the ♠8 (suit preference) to partner's ♠Q. She returns a diamond for you to ruff and you cash the ♣A for the setting trick.
South: ♠A ♥K109 ♦A98653 ♣J75
North: ♠KQ1093 ♥AJ86 ♦QJ ♣K9
This hand was another reminder of the importance of right-siding the NT bids. North opens 1♠ and South bids 2♦ (game forcing with 7 losers). North rebids 2♥, showing at least 5-4. South's proper bid is 3♦. Do NOT grab the NT with ♣Jxx—partner may not have anything in clubs. Partner will bid 3NT with a stopper.
If they lead a club which is likely, partner can go all out and take 12 tricks. Declarer wins the ♣K, the leader having the ♣A. Even if the ♦K is onside, you are missing the ♦10 and therefore also need a 2-2 break, which is only a 20% chance (50% × 40%). So you put your hopes in the heart finesse (and perhaps the ♠J will fall). So, over to the ♠A, and cash the ♥K. Then, run the ♥10. If it is ducked, continue with the ♥9 to your ♥J and ♥A.
If the ♥10 is covered, take your ♥A and continue with the ♥J, smothering your ♥10 in dummy since you have the ♥8 in your hand. Then cash top two spades. When the ♠J falls, you can cash two MORE spades. Your poor LHO is suffering greatly at this time. He is guarding both the diamonds AND the clubs (with ♣Jx remaining in Dummy). You have been discarding Dummy's diamonds on the fourth heart and on the spades. LHO, however, is likely to start discarding clubs—which will make it clear that he is guarding the ♦K.
At this point, LHO is probably down to ♦K10x ♣AQ in this position where RHO’s hand is immaterial but for the ♣10:
On the fourth round of spades, you discard another diamond from Dummy. If LHO discards the ♣Q, you discard one more club from Dummy. The fifth spade will be a killer for LHO. If he discards the ♣A, you discard a low diamond from Dummy. Then you take the diamond finesse and cash the good the ♣J in Dummy for all 13 tricks.
If instead on the fifth spade, LHO discards a diamond, you can only take 12 tricks. East will cover your ♦Q, forcing you to play the ♦A. You can cash the ♦J as the ♦10 falls from the LHO, but do not have another diamond to play to Dummy's good ♦9. So, depending on the defense, you take either 12 or 13 tricks with a club lead. Most of the pairs in NT got a club lead, but only 4 of them made 12 tricks.