For one move blunders, it is things like: - Look for checks. - Look for hanging pieces. - Be extra careful with knight forks. - Be careful with pawn forks.

For one move blunders, it is things like: - Look for checks. - Look for hanging pieces. - Be extra careful with knight forks. - Be careful with pawn forks. - Look for zwischenzug when doing exchanges. - Look for what a piece is currently doing before you move it (is it defending something?). - Apply above reasoning to what your opponent might do in the next move after yours. 2-3 moves ahead is mostly the same, just in a bit more depth where some common tactics come in, e.g. the bishop sacrifice on A2 if the white king is castled and stuff like that.