Defenders on Both Hands

K 9
A K J 10 8
K 6 4
6 5 2
J 5 4 3 2 10 6
9 Q 7 4 3
Q J 10 9 8 5 3
Q 8 4 A J 10 3
A Q 8 7
6 5 2
A 7 2
K 9 7

The hand was played in both no trump and hearts, and the maximum potential would seem to be 10 tricks. With the heart queen offsides, you only have four heart winners, 3 spades, two diamonds and a club, with the ace of clubs favorably situated. Some didn't make 10, a few didn't even make 9, but I was drawn to those who made more than ten, so I printed out one making 11 tricks in hearts, and another making 12 in no trump, though the losing heart finesse goes to the hand with the ace of clubs!
On the first hand, I didn't have to look far for that 11th trick. Opening lead was a diamond, won by the king and declarer now eschewed the heart hook for unknown reasons, cashing the ace, king, then playing the jack to the queen. On his first opportunity to sluff West "got rid of" two low spades! Though I haven't given the bidding because of two different contracts, in each South opened a minor and over one heart, bid a spade.
What more is there to say? Keep the same number in a suit as declarer has! Often this comes out as Keep the same number as dummy, but here it's keep the same number as indicated by a bid! What if I have to unguard a luscious holding like Q J 10 9 of diamonds? Yes. You want to keep at least three of those cards (well, two after the diamond lead), but if push comes to shove, unguard that suit before you unguard the spades.
I took a look at East's diamond holding and saw he does in fact hold the 8 and could guard the third round of the suit, except that . . .in one instance, that was his opening lead! In any event, the first discard of a spade is certainly tolerable and obvious. RHO doesn't figure to hold a five-card spade suit. The second discard can easily be a diamond or club. You're not squeezed yet. And the third? Well, clubs are ambiguous. It's hard to see if the queen will be of value or not. But better to discard all clubs in this ambiguous situation than to give up the sole guard to the fourth round of spades or the presumed sole guard to the third round of diamonds, no?
As you can see, West's club holding is completely useless here, and so there should not have been an 11th trick. He couldn't know that. But he should know that he cannot afford to give up his spade guard or 3rd round control of diamonds.
As for the person who made 12 tricks, well, obviously East didn't cash his ace of clubs when he had a chance, but let's see how declarer got 12 winners out of this where there would still seem to be only 10. The opening lead, with the North hand as declarer, was the jack of clubs, declarer winning with the king. So there's one trick without the inconvenience of losing to the ace. Declarer now took a losing heart finesse, got a spade return, which he won with the king. A spade return? The defense then had the capability of three quick club tricks to inhibit that common 10th trick for a good board. Anyway, after one more spade trick, declarer ran four hearts, and here are West's discards: The four of spades, the 9 of diamonds, the eight of clubs. So far so good. The ten of diamonds! Not so good. I have said elsewhere, guard the suit only you can guard. If you thereby uncover a winner in another suit, then you were squeezed, and there's no shame in that. But you don't want to finish the hand finding you're both guarding clubs and nobody's guarding diamonds, which is what happened here.
It's true that by chance, East could protect the 3rd round of diamonds with the 8 when West discards two of them, but it's an awfully hard card to communicate, and you get only one guess as to East's first discard: yes, it was the 3 of diamonds on the fifth heart! [I grant that it's awfully difficult to see that the 8 of diamonds could be a key card, allowing West to discard diamonds and save spades. But there's something a bit perverse about not leading clubs at trick 3 for three more tricks upon recapturing the lead, and then dismissing the diamond suit so as to save clubs! Yes, the defense would have to get past a potential blocking in clubs, but at worst would get three tricks.] So for all practical purposes, West should be saying, I've got to save four spades, based on the bidding and I've got to save 3 diamonds to guard against the third round, so that leaves only clubs! Again, he can't know that his partner has complete control of that suit, but if this uncovers a club winner, then you were almost surely squeezed. Further, this defender had a slight advantage over the previous one in that his partner led a club! So the second diamond discard is totally wrong, and along with his partner's discard of a low diamond allowed declarer an 11th winner. But there's still one to go!
Declarer now cashed a high diamond, cashed the queen of spades, the king of diamonds and overtook the 6 of diamonds with the 7. On that trick, West had a last chance to shine, even if rather dimly, but chose to discard the high spade (and remember there was a spade bid on his right) to keep the second highest club for trick 13! You go figure. And when you do, tell me what the second highest card in a suit can do for you at trick 13.