Picking Correct Captures
It's good to give the pieces certain point values based on how useful/mobile a piece is to allow you to understand when you are winning or losing in a chess game before checkmate actually occurs. As such know that the queen is worth 9, rook is worth 5, bishop and knight are worth 3, and pawns are the base unit of 1.
Note that you tend to prefer having a bishop and knight vs a rook and a pawn. Naturally also you can be down in material/points system mentioned above but have a strong attack/other positional redeeming qualities and win the game regardless.
Example of how this is applied in your thought process.
Above white is attacking both your queen on d8 and rook on h8 (naturally you can't capture the white knight on f7 with your king because it is defended by the bishop on c4). As the queen is worth 9 and the rook is worth 5, you would prefer to save your queen than your rook.
Above you have the option of taking the rook on h6 with your f1 bishop. As your bishop is only worth 3 points but your opponent's rook is worth 5, you should definitely take the rook.