Are any of Black’s pieces loose? Yes, the rook. White’s queen can attack it from d4 (and also from d7, but that’s unsafe), but not while giving check, and the checks Qc2, Qd3, and Qh6 all lose the queen. So look for ways to draw the Black king into harm’s way by checking it with another piece. White’s rook has a check in RxB. If Black replies KxR, then reconsider White’s attack on the loose rook—still the target. Now Qd4+ has become a working fork that wins back a rook and leaves White up a piece.