Case 1: Not Without Help

J 5 2
A J 5
Q 4 2
A K Q 5
8 7 4 Q 10 9 6 3
9 8 7 6 3
J 6 A K 9 5 3
10 9 8 7 2 J
A K
K Q 10 4 2
10 8 7 Contract: 4 hearts
6 4 3 Opening lead: 7 of spades

How do you avoid three diamond losers here, or to word it another way, how do you make a winner out of those 6 cards? The answer is you don't without help from the defense. But defenders found three different ways of allowing that trick.
A few declarers led low from dummy's holding, East hopping up and now whether East continues with his second top honor or lets declarer initiate the second round, declarer has a winner coming if he doesn't squander his 10. East has a tough decision there and guessed wrong, a tolerable misguess.
One West player went up with the J on declarer's first round low lead, a gratuitous squandering of that valuable honor, which is not so tolerable. Declarer covers, of course, and now can generate a winner by leading toward his guarded 10 when he regains the lead. But the play that caught my attention and which was repeated by several East players was the play of the 9 of diamonds on the third round of trump!
I wish there were a word for it: A defender signals some good stuff in a suit which is now not quite so good because of his announcement of how good it is. It's not all that rare. "Hey, Pard, I've some good stuff in diamonds. If you get the lead, how about a diamond to me, huh?" This was information West couldn't use, didn't ask for, didn't need to know -- and not least, cost the defense a trick!
For now declarer can lead the 7 or 8 and push it through if uncovered, and it takes one of East's top honors to win the trick. Declarer regains the lead and on low to the Q, picks up the J making the 10 a winner. The squandered 9 is -- or could have been and should have been -- a winner-enabler. It won't necessarily win a trick, if not squandered, though it could, depending on the various ways the diamonds could be played, but on right guesses by East that 9 will ensure that declarer does not promote a diamond winner. (West has no guess to make and shouldn't play the J first round unless he sees the 10.)

Case 2: A Favorable Lead, but Still a Problem

Q 9 8 7
2
K J 7 3
K 7 3 2
6 3 A 4
Q J 9 8 7 6 5 10 4
A 4 Q 10 9 6 2
J 9 A 10 6 4
K J 10 5 2
A K 3
8 5 Contract: 4 spades
Q 8 5 Opening lead: A of diamonds

Declarer was relieved of a guess on that opening lead, but still had his problems. He'd have to lose tricks to the A of spades and A of clubs, and the question at issue was whether he could avoid a second club loser.
West continued at trick 2 with another diamond, declarer wisely declining to trust his fortunes to a finesse there.
He now knocked out the A of spades, on a low lead to dummy's 7, and when East continued with diamonds, wisely ruffed high, West discarding the 9 of clubs. Declarer now drew the second round of trump, cashed the top hearts and ruffed a heart, led the J of diamonds, covered by East, ruffed by declarer, who now led a club to the K and East's Ace. East continued the suit, declarer finessing the 8, and when that held, he was home free.
The defensive loss of a winner-enabler is doubtless apparent. Declarer simply cannot avoid two club losers if West keeps his J 9. The J may not wind up a winner and the 9 may not wind up a winner. But if they serve to make the 10 a winner, they've done their job here. With seven hearts, West couldn't spare one of them rather than that 9 of clubs? Oh, he wanted to shorten the suit so as to get a ruff? Perhaps, though it hardly seems likely. Declarer's on lead, evidently with all the high trump after knocking out the Ace.
No, there isn't much excuse for pitching that 9 of clubs when there are so many hearts to spare.

Case 3: A Very Innocuous Card


J 7 5
A 10 8
K Q 6 2
A 6 4
10 8 4 3 2 Q 9
5 4 2 Q J 9 6 3
J 10 7 3
10 9 5 Q J 7 3
A K 6
K 7
A 9 8 5 4 Contract: 6 no
K 8 2 Opening lead: 3 of spades

Declarer ducked the opening spade lead in dummy, getting the Q from East, winning with the K. The Q was a goner anyway and declarer had luckily escaped the losing play of the J. Now he ran five rounds of diamonds, sluffing a low club in dummy, while West sluffed a card in each suit. Didja note a totally unnecessary discard that could have proved costly as the loss of a winner-enabler? Well, it was that innocuous-looking 5 of clubs!
For in discarding that card, he made his partner the only one who was guarding the third round of both hearts and clubs. And therein lies the makings of a squeeze. After 8 tricks (three spades and five diamonds), declarer could have gotten down to this position:

-----
A 10 8
------
A 6
10 8 ------
5 Q J ?
------ ------
10 9 Q J ?
------
K 7
------
K 8 2

Wherein with five cards left, East has been squeezed down to a doubleton in one of those two suits with a question mark. West, after one spade discard and one heart discard elected to throw that seemingly useless five of clubs at trick 6. How could the measly five of clubs do anything for the defense? Well, you see it above.
Now, this is not to suggest that a defender should've foreseen the surfacing of that squeeze position. I doubt if many players could have foreseen that. This simply isn't in the same ballpark as that flagrant and profligate signal with a 9 in Case One, nor with the careless discard of a 9 offering some protection to a J in Case 2. But if the discard of the 5 is a far more forgivable decision, I include this example partly to say, "Look at how a seemingly insignificant 5 as a second guard to a 10 can actually be worth a trick." From that, we just might expand our imagination ever so slightly. And coupled with that is the suggestion, the recommendation, that one would do well to start discarding totally useless cards before those with a chance of becoming valuable.
West could certainly have spared all three of his hearts, for heaven's sake. The 5 4 2 with three hearts in dummy all higher than the five? Declarer would have to stand on his head to find a way of letting West make use of one of those hearts. Surely a twice-guarded 10, though perhaps not likely, by and large, to be a player on the hand, is far more likely, infinitely more likely (if we divide by zero), to be worth something. There are indeed a number of ways a twice-guarded 10 can win a trick (partner has Q J tight, for instance).
To be sure, it isn't all a downhill coast. If West discards his hearts, he's going to be facing a difficult decision when declarer later leads two rounds of hearts (after 5 rounds of diamonds, without touching spades). He will be pseudo-squeezed. He can clearly afford a spade on the first round, but on the second round, does he save his clubs, for whatever a twice-guarded 10 might do, or save his spades, guarding against the possibility that declarer started with a 4-card holding in that suit? East could have helped his partner by discarding the 9 of spades (which he did not do). West may or may not have led from the K (from East's viewpoint), but the 9 can't do much for him, and that would have told West that declarer cannot have a fourth spade. So on five diamond leads, East sluffed two hearts and a club. By the same token, had West discarded 3 hearts, this would've given East insight to the heart distribution, in addition to allowing West to save his clubs,
"Okay, so he made a bad guess early instead of late," a cynic might protest. "How're gonna solve anything by putting it off?" Well, that's exactly it. You often do solve a lot by putting off the difficult decision. West threw that 5 of clubs at trick 6. If we presume that declarer would have proceeded in much the same manner had West discarded hearts, the second round of hearts, the crusher that puts West's feet to the fire, would have come at trick 10! That's a lot of tricks later out of a 13-trick game and not only gives West a little time to get his head in gear, but discards by either declarer or his partner might well clarify the hand.
At trick 7, there was a club lead, everyone following low, at trick 8, a heart lead, at trick 9, a club lead, East playing the Q! I'm not sure what message East intended, as opposed to playing the J, nor what West surmised, if anything. If he convinces his partner that he's now fresh out of clubs, that gives declarer K J low in clubs, and West's 10-high suit is no threat. In any event East now holds the top club -- and the ability to inhibit declarer from a third round heart winner. But when declarer runs two rounds of spades, East is genuinely squeezed and must give up the top club on the hand -- or his capability to inhibit a third round of hearts for declarer. That, of course is where West's potential to control the third round of clubs would have come into play.
In any event, even without help from East, had West discarded all his hearts earlier, by trick 10 -- the trick after East played the Q of clubs -- when declarer leads to the Ace of hearts in dummy, West just might see that his partner could be having trouble discarding and that the best thing he could do would be to keep clubs. Buying time, the span of four tricks, offers some hope.
There's no argument that these decisions should've been worked out by trick 6. Rather I'm suggesting that fairly competent players might reflect that that 3-card holding could be worth a trick and thus not discard from it until there are no more useless cards in his hand.
In real life, declarer didn't find the squeeze, having wiped out his communication in hearts at trick 10, the very trick where West would have had his feet put to the fire. But he found another error. At trick 12, with a spade lead from dummy to the Ace, and hence the end of declarer's access to the 10 of hearts, East sluffed the J of clubs instead of his last heart and declarer had his overtrick.