I have personally adopted a philosophy of "configuration assurance". I use it as the sort of "master caution" of person warning systems. It is totally simple:
I am going to change my phase of flight. Doing this may require a change in configuration of the aircraft. Have I assured that configuration? One might use multi page checklists, if appropriate to the aircraft type, or for very simple aircraft it might be a few memory items. But you will assure configuration.
The notion of "wheels down" before landing is generally good, however that is not the solution to prevent disaster when flying amphibians. I trained a very experienced pilot to fly an amphibian. I had to train out this "check gear down" thing in his head. I trained him to check that the wheels are where they must be for what he plans to do next - the required configuration. I have certainly flown 182's 185's and Caravans in which the wheels better be retracted before you land!
For most GA planes, the items which if over looked, will result in some degree of disaster, are few - wheels and fuel are probably the biggest ones. So just get your head around assuring that those few items are appropriate to what you're about to make the plane do. Don't be lazy and wait for some kind of warning system to hopefully work, and remind you that you have forgotten - be ahead of the plane, and the warning systems! Do it yourself!