This one is harder. A scan for loose pieces turns up the bishop on e2. White’s queen can attack the bishop and check the Black king by moving to e6; but e6 is protected by the knight at f8. White can’t capture the knight, and there is no way for him to draw the knight onto e6 so that the queen can capture it and execute the double attack at the same time. Is there any other piece the knight protects that could be taken? No. Well, when in doubt, play with other checks you can give and their consequences. Consider Rg5+. Notice that White’s queen greatly constrains the ability of the Black king to flee such an attack; indeed, the king cannot be moved at all. Black’s only option is Ng6, interposing his knight between the rook and king. With the knight thus budged from f8, the way is clear for White to play Qe6+ and win the bishop.

It's hard to overstate the value of looking at checks and their consequences.