I must include one of the classics: GUMPS.
G as on fullest tank, and boost pump on
U ndercarriage (gear down and locked)
M ixture full
P rop to takeoff pitch
S witches and Seat Belts (landing lights, etc.)
A good suggestion for those of us who fly with the gear “down and welded” is to press the toe brakes on the U to make sure there’s hydraulic pressure. I also like to say “gear down” while reaching up to pull down a phantom switch. I figure it can only make the transition easier.
Some learn it as CGUMPS, with the C meaning carb heat.