I want to thank you beforehand for taking your time to read and (hopefully) answer this. My question is a bit ambiguous, so I'll give an example. Let's say I'm playing white, the enemy has castled king-side so his king is on g8, with his rook on f8, and his knight is on f6. Also, he's got his three castle pawns at their original positions. My dark-square bishop is fianchettoed and I can thus trade it for his f6 knight. If he can only take the bishop with the g7 pawn, opening up his king, when is it a good idea to trade (i. e. what other factors affect if it is a good idea or not)?
[FEN "5rk1/5ppp/5n2/8/8/8/1B3PPP/5RK1 w - - 0 1"]