Hands are from Soledad Club, September 17, 2018.
South: ♠KQ1053 ♥Q10 ♦K83 ♣J84
North: ♠J2 ♥J7 ♦AJ1075 ♣A872
Partner as North elected to open in third position. (I would have passed because it is a minor-suit oriented hand. I do not like to open light without the majors. I'd rather the hand be passed out than have the opponents get to two of a major and make it because I opened the bidding) So, the auction went, 1♦-P-1♠-P; 2♣-P-2♦-P; P-2♥-P-P. Now partner was stuck by LHO’s balancing 2♥ bid, so she took the push to 3♦. We received the fortunate lead of the ♠8, which went to RHO's ♠A. West returned the ♥4 to LHO's ♥A. LHO continued with the ♥5 back to RHO's ♥K. Now RHO led the ♣5. Partner properly rose with the ♣A, RHO playing the ♣3. Two problems remain: trumps and getting rid of those club losers.
Partner has several clues: (1) the club honors are divided because RHO played a low club (promising an honor) and would have led the ♣K if she had both of the missing club honor. Club are probably 3-3, based on the spot cards, but RHO could have four and LHO a doubleton honor. (2) hearts appear to be 6-3. RHO led the ♥4 (from either three or four cards), but LHO returned the ♥5 after taking the ♥A. The ♥2 and the ♥3 are MIA. So, if LHO returned original fourth best (standard carding) after taking the ♥A, LHO started with six hearts. (3) There is more room for diamonds in the RHO’s hand than LHO’s hand. (4) LHO did not overcall 1♥ (or 2♥) at her first opportunity, despite having a 6-card suit to the ♥A and either the ♣K or the ♣Q. That is an argument for LHO having the ♦Q as well as the other cards already known.
So, there is a strong argument for going to the ♦K and then finessing West for the ♦Q. However, if the bridge gods tend to laugh at you and put doubleton Queens in against you, another line is to cash the ♦A and the ♦K. If the ♦Q doesn’t drop, it is most likely in RHO’s hand. However, RHO’s hand probably has four spades, based on the opening lead. So, you can discard two club losers on the third and fourth rounds of spades. Then, you discard your last club loser on the fifth spade as West ruffs with the good the ♦Q. I will leave it to math mavens like Matthew Kidd to figure out which is the superior line.
Dummy: ♠Q106 ♥K2 ♦10754 ♣KQ94
Declarer: ♠A52 ♥A1064 ♦AK63 ♣86
You open 1NT and quickly find yourself in 3NT with the lead of the ♣4. Since the opponents have sever cards in each major, yet did NOT lead a major, you suspect that the lead is from a 5-card suit and that LHO probably has the ♣A, so you rise with Dummy's ♣K which wins.
Timing will be tricky here. You have to give up a diamond to develop the suit. You will have to guess the spade suit correctly (whether to play for ♠K or ♠J on your left) because hearts are unlikely to provide more than two tricks. And, you'll have to lead another club toward Dummy eventually, to develop a second club trick. You canNOT do the club immediately because if you win the ♣Q and then play spades, if West has the ♠K he can then take three club tricks along with the ♠K, and you'll still have a diamond loser.
My partner asked me how I “knew” which spade to play from Dummy. I told her it was a guess (which is true). However, I am going to tell you a “trick” of the pros that can help your guessing in similar situations: switch suits when you have a suit with a guess. Play the ♦7 to your ♦A. Cash the ♦K, calling from the ♦10 in dummy, unblocking to keep a diamond entry in your hand. Now play a low spade toward Dummy. LHO will NOT be expecting a spade. He's been following in diamonds. If he has the ♠K, he is likely to think a little bit longer about what to do than if he has the ♠J. [Of course, superlative defenders decide when Dummy first comes down what they are going to do in these situations so they will NOT be caught off-guard and reveal something by their tempo.] Dummy's ♠10 forces the ♠K and you are OK. Since LHO played the ♦Q on the second round of diamonds, you are fairly sure that RHO started with ♦Jxx in diamonds, so even if East returns a club to knock out the ♣Q, that will be his last club (the ♣10, in fact, as LHO would have led the ♣J from ♣AJ1043), so when you give up a diamond to East, he cannot reach his partner. You take two spades, two hearts, three diamonds, and two club tricks.