Now the same idea from Black's side. White has just made a capture that left his knight loose in the middle of the board; he thought the e5 square looked safe. But with the d2 and c7 pawns both moved, see how Black’s queen can check the White king and attack (and win) the loose knight with one move: Qa5+. Study the pattern of open squares on the d and c files here so that it is visually familiar to you.

Generally speaking, the most striking early tipoff that a move like this may be possible is the movement of pawns on the c or f files. Movement of the d and e pawns early in the game is common; early movement of the c or f pawns is a little less standard, and so should jump out at you as creating the possibility of moves like we see here.