I follow Fred's note to leave the hand on gear selector until three green.  It comes from my experience in a twin, I raised the gear and did not check the lights--the pump kept running and melted the safety tube thereby draining the entire hydraulic pack and requiring a return to base with emergency extension.   Had I kept my hand on the selector (both raising and lowering) until confirming correct signals, I could have pulled the breaker and saved the system.

The tow bar never stays on the plane--ever.  Twice burned with that one.

The canopy gets tested with a hard push up before entering the runway--lesson learned from LML.  It is now habit.

I check the gear selector is position down before climbing into the cockpit.  From experience.

I use red ribbons on anything left unfinished so I don't forget before the next flight.  from experience.