Immediate Decision

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

Opening lead the J of hearts. Declarer has an extra heart honor there. Does he pitch a club and inhibit any chance for two losers in the suit or a diamond, also inhibit the possibility of two diamond losers? I'm going to hafta say it should be a diamond, on this ground: there are no more entries to dummy, and even with an onsides A of diamonds, you might find yourself coughing up two diamond losers if East goes low and the K holds -- whereas you don't need another entry with an onsides Q of clubs.
Obviously with the discard of a low diamond and subsequent finesse of a club, I open myself to a charge of hindsight, which I'll hafta leave for the reader to decide for himself. But one thing is certain. You wanna do one or the other! This declarer did neither and went down. Actually, had he done one or or the other, he would at least have made his contract.
Say he discards a club. Now he's going to lose two diamonds and one club. Or he discards a diamond, he's going to lose one diamond and either one or two clubs, depending on how he plays that holding. Either way, he has his contract at least.
The holding of a low doubleton opposite K J low low will be frequently encountered. And assuming you have no sluffs of the two-card holding in the closed hand, it's a tossup. If the A & Q are in the same hand, it doesn't matter what you do. And if they are in different hands, it does matter, and you may want to play either defender who's shown the most strength for the A. But it's a mere two-point difference you're talking about, and given the variety of aggressiveness vs. caution among players, I would be very skeptical about finding much leverage on that count (not to mention the times that neither or both opponents have shown some strength).
Here, it's not K J, but with the 10 showing with the K opposite the J in the closed hand, it amounts to the same thing. So even if declarer rightly sluffs a low diamond on the second heart honor, he might miss his chance for an overtrick by misguessing in clubs. But still you make. This declarer not only didn't discard anything on the second heart, to which he has no (sure) entry later, but guessed wrong on the clubs, losing two diamonds and two clubs.