Our drill used to be looking for checks. Now it's looking for loose pieces. (In practice you want to do both, of course.) Here Black’s bishop is loose, so look for some way to attack it and give check. The queen can’t attack the bishop with any of its available checks: Qf8, Qh8, Qe3, and Qxg6. But examine the consequences of those moves and you find that Qh8+ forces Kg5. Remember the goal: to attack the loose bishop and give check. Would that be possible from the new position on the board? Indeed: Qe5+ then forks king and bishop and wins a piece. Ideally you want to see this in one visual motion. Imagine checking the king with your queen from h8, and see the king move to g5 in your mind’s eye; then see it aligned with the bishop, enabling you to play Qe5+.