Figure[White to move]

Here White has three checks with his queen that result in its uncompensated loss; but he also has Bh5+, which is safe and interesting: it requires Black to move his king over to d8. When you see a move that will force the king to change squares, ask whether anything will be pinned to it in its new position. A cursory scans reveals that the pawn on d7 will be pinned. Next step: ask whether the pawn is supposed to protect anything that might now be vulnerable. Answer: Black’s queen on c6 is loose. There is a complication, though, because the only piece White can use to take Black’s queen is his own queen, which also would be the piece imposing the pin; once White plays QxQ, will the pin of the d7 pawn still be effective? Yes, because the rook behind the queen takes over the pin once the queen moves.

The idea here, though only one move away, is not easy to see at the start. It promptly becomes visible when you play with checks and their consequences.