Interesting

A K 9
A 9 8
A Q J 5
10 4 2
5 J 8 6 4 3 2
J 10 6 2 Q 7 3
10 9 8 2 7 6
Q J 8 7 9 6
Q 10 7
K 5 4
K 4 3 Contract: 6 no trump, maybe 7
A K 5 3 Opening lead: 10 of diamonds

An interesting hand on several counts: 42 declarers, all but one in no trump, and all but two of those in slam. Nine were in grand slam, three going down 3 (!), four going down 2 and 2 down one. Thirty were in little slam, twenty down one, 10 making. I had to find out why.
There are three basic reasons, I figure, for a discrepancy in number of tricks garnered: Declarer misplay, defensive misplay and simply a bad guess in a difficult situation. First I counted the hcp's, not that that should necessarily be the deciding factor, but it might tell me something. And bingo! The magic figure of 33. Then I looked at the hand and found that there's simply no way to make 12 tricks against best defense. If clubs split 3-3, declarer would have his 12th trick, and failing that, there might be a squeeze, which can only be a club-heart, since spades and diamonds are solid. But no, West must protect clubs as East protects the third round of hearts, so there should be no squeeze. So how did those 10 declarers make their contract?
The very first one I looked at turned up with a low heart opening lead! Do you know what that means? East has to play the queen, and yes, now there is a squeeze against West as the only one who can protect both clubs and hearts, and declarer played it very well. The first step is to lose a club. You lose a club in part because there might be a 3-3 split and in part because there may not be a 3-3 split, but you must lose a trick to rectify the count (get in a position to win every trick but one). Declarer cashed the ace of clubs (perhaps to see if clubs were Q J tight?) and then lost a club. Back came the jack of hearts, knocking out the ace, declarer ran his spades and then his diamonds. On the last diamond at trick 11, West let go his club guard -- he could see the 9 of hearts in dummy and followed the principle of guarding the suit only he can guard (at that point), so declarer went to his clubs for the last two tricks. Well done.
None of the other nine defenders led a heart, but three led a club, which was just as devastating. Curiously, one led the queen of clubs which held! Declarer could have won and led to his 10 immediately for a 12th trick. Now if West had simply backed off and led anything but a low heart or low club, they would have had declarer where they wanted him. But he didn't and now led the 7 to the 10 and declarer made in that way. So in the first 5 cards played, there were three errors.
West said, here's a club lead that'll allow you to make and declarer said, no, I don't wanna take advantage of it, and West said, no, go ahead, take your third club winner. Two others led a low club, allowing the 10 to win. Which leaves six declarers who got neither a club nor a low heart opening lead and still managed to make. How is that?
Well, lemme see. Here's one where West began with the 10 of diamonds. Declarer ran four diamond winners and two spade and West felt squeezed, throwing the wrong card. Can he see that? I don't see how. Couldn't declarer have 4 hearts and 3 clubs? In that case a low heart could hand declarer the contract while a low club is safe, and I don't think West deserves any censure there.
One led the 5 of spades. Declarer rightly ducked a club, for reasons already given, and got the Q of clubs back. Now at trick 9 West discarded a club and declarer could see that he had his 12th trick, since two rounds had already been played, so the discard meant there was only one more club out. A little curiously, on the next trick, East discarded a low heart in order to save a totally useless spade. After all, three rounds had been played, and it should have been obvious that declarer had no more to lead or protect against. Had West saved his clubs and gotten down to two hearts and had East still discarded a low heart, declarer could have picked up his 12th trick in hearts. And there's no reason to suppose East would have done otherwise, since discarding a second guard on a twice-guarded queen to save a useless spade makes neither more nor less sense in that situation. On the last trick, the five of clubs won as West protected hearts and East spades.