I fly an Arrow III. There are a couple of good simple checks/reminders:
Take-off: after a reasonable climb-out, don't do anything until the gear is sorted: "Postive rate: gear-up" is what I say to myself. The gear only goes up when no runway is left.
Use the gear as a drag flap: To lose significant speed, put the gear down. This is useful on a downwind/approach. 21/25 as the setting with gear down should bring you to about 100kIAS.
Approach and Final: say to yourself: "All the Reds, All the Blues, All the Greens": Physically check the levers are fully forward, and look for the greens. The other useful thing to say when talking to ATC is: "G-XX is final with three greens" and look at the greens. I also do one last chance saloon check at about 200 ft.
Another useful saying: To go faster: "Revv-up": i.e. prop-speed. Slow down: "Throttle back" i.e. manifold pressure.
In a dark cockpit, make sure you are moving the correct lever. I started pulling back the red one on climb-out once, and thinking: that's strange...
I tend to keep power on just before touch-down. There is an art to it however, and it takes some getting used to.