A Marked Finesse, Anyone?

A K 7 5 2
9 7
A 9 4
A 9 4
Q 9 4 3 J 10 8
10 5 3 2 J 6 4
J 10 7 2 8 5
2 J 8 7 6 3
6
A K Q 8 Contract: 6 no
K Q 6 3
K Q 10 5 Opening lead: low spade, low heart

Declarer has 11 top tricks in this 6 no contract, and a couple of declarers wound up with 11 tricks for down one. Yet there was ample opportunity for a 12th trick, starting with a marked finesse if only declarer will take care to play for one. The clubs should be begun with the K (or Q) and then to the A for just that situation that exists. If by any chance RHO is out of the suit (and it has been known to happen with 6 cards), you've a marked finesse against LHO. But both show up. So now you go to the A and you find LHO is out and you've a marked finesse against East for a 12th trick. To be sure, you've still got the opportunity to take the marked finesse if you cash the A and then go to the K -- provided you have an entry back to dummy. So probably all is not lost. Still, it saves an entry if you start with the K.
One declarer got a heart lead and promptly cashed the top spades (sluffing the 8 of hearts). Whoa! You don't need to cash those top honors until you're in dummy for the last time. There's no reason to. You're not going to inconvenience the defense and you do inconvenience yourself, for you don't know what to throw on the second spade! It's true that hearts are the only remaining suit not 4-3, with a chance of making a long-card winner on that fourth card. But you also have an outside chance of dropping the J and 10 in three leads, making a winner out of the 8, and declarer should be open to these possibilities insofar as convenient, and here there's really no inconvenience in holding off from cashing the spade honors. You might also get a careless discard from the defender with the long hearts, which wouldn't be the first time for such a careless discard. Hence, win the heart opening lead, run your four clubs by the sequence cited above, cash your remaining top hearts and go to your spade honors.
It looks as though you'd have a squeeze if the hands were reversed, but they're not and West is discarding after you on that second spade honor. But then, you're discarding from the closed hand and West might have a tough time deciding what to do. Anyway, you'd want to discard the 8 of hearts, if you're certain it isn't high, since you might get a 3-3 split in diamonds, and it's now out of your hands.
Indeed, you have a pseudo-squeeze there that a lot of defenders will fall prey to. On four club leads (with that marked finesse for a 12th trick, of course), the best thing West can do is to discard all spades, counting on East to save the spades. But do you think every West is going to discard the queen-high suit to save a jack-high and a ten-high suit? I doubt that very much.
So declarer's play didn't augur well, as is often the case. A of clubs, club to the Q. No sweat. He's got a re-entry in diamonds, no? Back to the A of diamonds, diamond to the Q. Diamond to the queen! So now he's used up that entry without taking the marked finesse, as he'd needlessly used up the spade entry earlier. Develop, develop, develop! Anybody can cash 11 tricks here, yes, a novice in his first day of bridge.
The other declarer got a spade opening lead, and promptly cashed the top three hearts. I wouldn't move on hearts so quickly and alert West to hang onto the top heart. But a better reason for holding off on the hearts is that they can't split right (though J 10 low could fall in three leads), whereas either minor suit might split right. Anyway, he now came to the A of clubs (shoulda been the K first!), cashed the second spade honor, throwing a diamond. That's wasteful. Well, on this hand, not so literally wasteful, for diamonds aren't splitting 3-3, but declarer doesn't know that and should test them first before cashing that second spade honor. So it's another play that doesn't augur well.
He now cashed the A of diamonds. The ace of diamonds! Now only a not-yet-marked finesse in clubs could save him. But of course he didn't take it and went down as a result. Sheer squandering of resources.

I think it a poor practice to count on defensive misplay and especially so when you have a viable path. Even when you get the misplay for your contract, it doesn't do much for honing your bridge skills, and when you don't, which I dare say is far more often the case when you plan on it, you don't do much for developing a partner's respect for your skills. Above I referred to a pseudo-squeeze which the defenders might avoid. But at no time did I advocate side-stepping a viable path to an overtrick so as to rely on a misplay. I've advocated nothing that would cost you. And I've certainly seen a lot worse discards than West, with 3 four-card suits, throwing from a 10-high or J-high suit to hang onto a Q-high suit that his partner can control (on the run of clubs). So I'm only saying it would pay declarer to watch the discards and act accordingly.
But of course the main point is handling the clubs correctly for a 12th risk-free trick. The rest is only for an overtrick and of not near as much importance.