The one that I've heard from multiple sources is "CCA". Looks for Checks, Captures, and Attacks. Looking for these for both you and your opponent can be incredibly helpful.
Another thing is to pay attention to every pawn move. Each one frees up squares that were previously defended, so there are potentially new vulnerabilities to exploit.
Pre-move checklist

Hi folks
Do any of you have a checklist you go through before making a move? I could really do with a system to help me avoid silly blunders or missed wins.