A proper walkround and inspection, and to actually LOOK at the fuel sample, and sometimes even smell it if it looks iffy!
NOT to tighten the engine dipstick with several metric tonnes of force......I hate having to use Stilsons to undo the cap.
NOT to say "Speed Checks Flaps One" when the airspeed is clearly above VFE
NOT to have curry and copius amounts of Old and Grungy the night before flying in a confined space with me.
But all pretty minor stuff anyway.....
Cheers