All I can say is the usual things like toilet paper, enough freshwater in the tank to make it home, make sure all vents/ windows are closed. Make sure your blinkers and brake lights are working and that the sewer outlet is hanging out the back and not getting crushed by a larger flatdeck truck when lowering it down.
A good thing to do is to not use the typical inexpensive hardware store turn buckles. Two of mine cracked on its maiden voyage home because the dealer used those to save money. I was shocked when I saw them after an 18 mile run home with a new camper. Good to get out and check them for proper hand tightness after a few miles of your first run.
BTW, I don't like horse mats because of their extreme heaviness when handling them for cleaning. I use a truck bed matt in strips that I can roll up/ easily handled.
Make sure the camper has enough height to clear the truck cab, bring a tape measure, as you need a minimum of a couple inches clearance between cabover and truck cab between there. You need to call the dealer and find out what the dimension is from camper bottom to the cabover sleep area bottom and then go measure the truck to make sure. Some have had to build a frame to space the camper up off the bed some to clear the cab.
Others will add to this for you as well.