Peter Drucker, a management consultant who was born in Austria, wrote, "Long-range planning ... does not deal with future decisions, but with the futurity of present decisions."
In bridge, sometimes you can delay the key move until well into the deal, after you have gained more information than you had at the start of the card-play. But sometimes, you need to spot the winning move immediately; one thoughtless trick and it will be too late.
When do you decide which is relevant on any given deal?
At trick one. When the dummy comes down, stop to do some analysis, counting high-card points (numbers you are honing after listening to the bidding), winners and losers.
In this deal, how should West plan the defense against four spades after he leads the heart jack to the seven, two and queen?
North responded with the Jacoby two no-trump, showing at least game-going values and four or more spades. South jumped to four spades to indicate a minimum with no singleton or void.
West has 8 points, dummy holds 16, and declarer presumably has at least 12. That leaves at most 4 for East. Which useful card could he have?
There is only one -- the club ace. But West must realize this very quickly because South has immediately won the first trick and led a low trump. West should ask for a timeout after the dummy comes down, refusing to let the declarer rush him.
West must win with the spade ace -- no second hand low -- and switch to the club king -- bingo!