With White’s knight and Black’s king and queen all on light squares, conditions seem right for a fork on f6. Is the square protected? Yes, by the Black bishop on e7. If White tries to first capture it with his own bishop, then Black recaptures with his queen and the fork is ruined. But again the trick is to imagine the fork, mentally placing the knight on f6 and not on e4. Then you can see that once the knight moves, the Black bishop becomes pinned to Black’s queen by White’s queen—another “discovered” pin. The point repeats: don’t just ask whether moves are possible; picture moves, visualize whatever countermoves seem to make them impossible, and ask what would then be possible if the countermoves were made.