Micro Soft Excel;
List of actions in order on left
Columns of boxes on right
Clipboard and felt tip pen
Date at top; check in every box before the trailer moves.
I have one for inside the unit (Shower door secure; Counter clear; etc) and one on the back of the sheet for outside (Water hose; Antenna; etc)
Since it is on a spread sheet it is easy to edit to reorder the steps or add an item.
I print 4 or 5 sheets front and back before each trip and hang the clipboard on the coat hooks by the door.
If I had to walk back to the truck to check the steering wheel or sun visor to see what needed to be done, it ain't gonna happen.