Your RHO opens 1C in first seat, and your side stays out of the auction. The opponents bid
1C - 1H;
1S - 2D!;
2N - 3H;
3N - P.
Upon querying you find out that 2D was an artificial game force. Before you make the opening lead, you try to reconstruct the opposing hands.
RHO opened 1C, rebid 1S, showed a diamond stopper, and denied any heart support. It seems like he holds 4135 (possibly 4144 with great clubs and awful diamonds).
LHO responded 1H, forced to game, then rebid his hearts even after his partner denied holding three. So he must have six hearts. Not much more is known about his hand (except that he's wildly unlikely to have four spades). Let's give him a tentative 3622.
If those are the shapes of the unseen hands, what does that leave partner? Three spades, two hearts, five diamonds, and three clubs (3253).
(By the way-- if you don't do something like this before your opening leads, you should try it. It's amazing the things you can figure out before seeing any of the other 39 cards.)
So now that you have a reasonable picture of the unseen hands, what should you lead? Diamonds feel right; they're your side's probable eight-card fit. So which diamond? You decide that it's probably right to start untangling the honors. So which one - the queen or the ten? It's just barely possible that LHO is 3613 or 3712 with the singleton jack of diamonds, so you decide to table the queen of diamonds. Dummy comes down and you see:
Almost what you had constructed, except dummy's singleton honor is in clubs. Declarer plays low from the table, partner plays the three (upside-down attitude), and declarer wins with the king. What's going on here?
Normally, you'd expect partner to hold the ten of diamonds to be signalling positively when you lead the queen. You hold the ten, though. So your lead has worked fairly well and hit partner with a diamond suit headed by the jack! That's great news... but we haven't taken five tricks just yet.
Declarer leads a heart toward dummy. You play low smoothly (of course), declarer sticks in dummy's nine, and partner wins with the queen. The nine of diamonds comes back from pard. Continuing your trick-one plan, you unblock the ten. Declarer lets you hold this trick. You exit your third diamond and partner plays the jack.
Dummy's now in and exits a high heart to your ace (partner following, declarer pitching a spade). Now what?
What's going on in the diamond suit? Does pard only have three diamonds himself? Did we just set up declarer's fourth diamond? You put yourself in partner's shoes. With an original J93, would you return the 9 on the second round from a holding of J9? You don't think so. It's much more likely that partner held J983 and is giving you a suit-preference signal for spades. But that's not all-- since partner is flagging a spade card, he won't have anything in clubs! If you don't cut transportation now, declarer can get at least three club tricks to go with two diamonds and four hearts. So you table a spade, and declarer sighs and concedes down one. You pick up ten imps for your trouble, as your teammates are +420 in hearts. Here's the whole hand:
This hand was defended in this fashion at the table by my lovely wife Meg. We went on to win the event. Well done!