Playing on BBO today, I held: ♠A 4 2 ♥Q 6 ♦Q 5 4 2 ♣A Q J 10 and opened 1NT. My robot partner tranferred to 2♠ and rebid 3NT. I corrected to 4♠ which ended the auction.
West led the ♦10 and (see below) this was the dummy:
How do you tackle this hand at matchpoints?
Well, the first hurdle is at trick one. You must play the king from dummy. Do you see why? If you do, East wins, but can't continue the suit -- the ♦9 in dummy will win the trick if he does.
East shifted to a club, and I finessed. West won and shifted back to diamonds by leading the ♦7. Those robots are relentless, aren't they? I won and played two more rounds of clubs, discarding dummy's losing diamond. Now what?
There are still traps. According to Deep Finesse, you will still go set if you lead any heart or the ♠A. I played the ♦4 and ruffed in dummy to lead a low heart to my queen. West won and switched to the ♠7 taken in dummy with the 10 (a different return wouldn't matter).
It was easy now for me to play the ♥K and ruff dummy's losing heart. I cashed my ♠A and with two tricks left, dummy had the ♠K J sitting over West's ♠Q 5. Making 4♠ was worth 89.7%.
Playing a high diamond at trick one is a common theme that most players don't see. In chess they call it gaining a tempo, but it applies at bridge, too.
Here's another common situation that's similar: Dummy has Q 10 2 and you have A 4 3. West leads the 9, you put in the 10 and East plays the jack. If you duck, East must shift which may give you time to develop a discard. All this assumes, of course, that West isn't getting tricky by leading the 9 from K 9 x.