White’s bishop can’t give a check and can’t safely threaten anything. But it can make a capture: Bxd5. Don’t just reason that it loses a piece to BxB; look for patterns that might form the basis of a tactical idea. On d5 the bishop would be aimed at Black’s king and rook, though its path to each piece is blocked. Again, a visual way to see the tactical possibility is to note the classic king-and-rook triangle that would lend itself to a fork at d5 if only the white rook and black bishop could be cleared out of the way. Pick either obstacle and think about how to get rid of it. If you start with the rook at b7, you need it to vacate its square in a violent fashion that requires a response and gives the enemy no time to regroup. The obvious solution is a capture: RxB, to which Black replies KxR, which takes care of both problems. Now Bxd5+ wins the rook. Or start your thinking with the Black bishop at f7. The natural way to get rid of it is by capturing it; and the only way to do so is with RxB, which again leads to KxR and the bishop fork from d5.