Visualization

Know the Contract. It's no accident that the final bid is called a contract and the process of getting there is an auction: that's exactly what it is:

N: "If I can name Spades as trumps, I bid 8 tricks for this contract" (2ª )

E: " I bid 9 tricks if Clubs is trump" (3§ )

N: " OK, I give up: Clubs is trumps - but you have to take 9 tricks" (Pass)

Count Your Winners. The most basic idea for defenders to consider is the tricks in their defensive contract: the difference between the declarer's contract and thirteen. (At 3§ , 13 - 9 = 4 tricks in the defensive contract).

Against competent bidders, the stopping point is an approximation of the number of tricks declarer thinks he can take and the number he thinks your side can take on defense.

Make the Declarer's Plan Your Own. Declarer, after the dummy comes down, looks at his losers and makes a plan to eliminate them or maximize the numbers of tricks in some other way. You can do the same by visualizing where declarer is looking at his losers: they are your winners. If your side bid Spades but the other side becomes declarer, remember that they heard your Spade bids and outbid you anyhow. Your defensive tricks won't all come from Spades, so you must visualize where the others will come from.

What Didn't They Bid? You can get a good start at this visualization by considering what your opponents did not bid.