Figure[Black to move]

Start with a routine inspection for loose White pieces; find the bishop at c1 and rook on e8—and then focus on the bishop. Black has no checks that also attack the piece, so he plays with other forcing moves. He has only one capture to consider: BxB, to which White would respond KxB. When you ponder such an exchange, think about what pieces would be left loose and what lines would be opened by it. The answer to the question about loose pieces is that the king’s move to h3 would leave a loose knight on h1; the answer to the question about open lines is that taking the Black bishop off the board opens a clean line for the Black queen to g1. Put these points together with the loose bishop at c1 and we have an easy double attack against two loose pieces: Qg1 wins the knight.

Notice how the same principles emerge time and time again: keep track of the loose pieces on the board, but also the pieces that are left loose by any forcing sequence you can find, no matter how short; likewise keep track of the open lines left behind by any forcing sequence you can find, no matter how short.