I was trained from my very first lesson to ALWAYS use GUMPS. Three times: downwind, base, final. No matter which a/c I'm flying, retract or not. That way it becomes a totally ingrained routine that will - hopefully! - prevent a gear up.
Btw, I agree with Pace re the horns and whistles. On Cessna RGs if the microswitches are just a tiny bit out, this will give you spurious warnings which you very quickly learn to ignore.