1. If someone shows out, play five rounds of clubs, discarding a heart and a spade from dummy, and cross to a high spade. If an honor falls, play a second high spade, and if the other honor falls, you have 12 tricks without needing the diamond finesse. If the other honor doesn’t fall, run the ♦J. If no honor appears on the first spade, run the ♦J. Notice that you cannot afford to cash a high diamond first because the suit is blocked if the jack is covered on the next lead of the suit.
2. If clubs are 4–1, draw trumps discarding a heart from dummy, cash the ♦A and cross to a spade. If an honor drops, play a second spade hoping the other honor drops. If doesn’t, run the ♦J. Given this scenario, you can afford to cash a high diamond first because you have a trump entry to your hand if the ♦J is covered.
3. If clubs are 3–2: Cross to a spade and assuming both follow low, play a second high spade. If both follow low, ruff a spade. If spades are 3–3, cash the ♦A, cross to the ♣K, discard a heart and a diamond on the established spades and take the diamond finesse for the overtrick.
If West follows with an honor on the second spade, lead the ♠10 from dummy. If East plays low, discard a heart. If West wins the queen, you have the balance as both of your low diamonds go off on dummy’s spades. If West ruffs and exits a heart, you are reduced to the diamond finesse after cashing the ♦A. If West discards on the third spade, draw the last trump and run the ♦J. It’s dangerous to cash the ♦A first with West having two black doubletons: West could have six diamonds! If West has a singleton ♦Q (what you are protecting against), West has started with eight hearts!
If East follows with an honor on the second spade, lead the ♠10. If East covers, ruff, and you are playing for an overtrick. If East discards, discard a heart. If West wins and does not have the odd trump, West must play a spade allowing East to ruff, forcing you to take the diamond finesse after you overruff. If East errs and leads a heart, you have the rest. If West has the odd trump, there is nothing West can do to prevent you from using both of dummy’s established spades to discard diamonds.
Thanks to Jonathan Weinstein of Princeton NJ for this one.