Start by noticing two facts: Black’s king and queen abut one another on the d-file; and the d-file is half-open, meaning that White has no pawns on the line and so can place a rook or queen on it and attack whatever lies at Black’s end. The hard and important thing is to avoid being distracted by Black’s pawn on d6; it is an obstacle to executing a skewer, but mustn't be an obstacle to seeing the potential for one. The objective is clear: get the pawn off the file. How? The usual way to clear a pawn is to take something it protects. Thus White plays RxN; and if Black replies d6xR, Rd1+ has become a working skewer, winning the queen when the king moves. White ends up with a knight and queen in return for two rooks. Again, RxN was White’s only capture of a piece, and Rd1 was among his only checks afterwards (all of which were on the d-file in any event). So faithful use of first principles leads to the same outcome.