Setting up a long suit is a basic technique. But even if you establish long cards, you need an entry to reach them. Keep your entry situation fluid.
At four hearts, South counted nine easy tricks: six trumps and three sidesuit aces. His best chance for one more lay with dummy’s long diamonds, so he cashed the ace and conceded a diamond.
East won and led a club, and South took the ace, led a trump to dummy and ruffed a diamond high. When
West discarded, South was sunk. He could lead a trump to dummy and ruff another diamond to set up the fifth diamond, but dummy lacked another entry to cash it. Down one.
South’s entry situation was fluid, but he let it go down the drain when he prematurely took the ace of diamonds. At Trick Two dummy must lead a low diamond.
If East returns a club, South wins, leads a diamond to the ace, ruffs a diamond high, goes to the ten of trumps and ruffs a diamond high. He can draw trumps with the A-K and take the good diamond for a 10th trick.
You hold: ♠ A7 ♥ K102 ♦ A6543 ♣ 7 6 4. The dealer, at your left, opens three spades. Your partner doubles, and the next player passes. What do you say?
ANSWER: Your partner’s double obliged you to respond at a high level (rarely, you might pass for penalty), so his hand is worth 17 or more points. He suggests support for all the unbid suits. Since you have 11 good points, you must commit to game. Bid five diamonds or (my choice) 3NT.