Your RV serves a variety of purposes, but when you need to transport a RV, secure all doors and windows by taping or tying them down. This includes cabinet doors in the kitchen and bathroom.
Remove all hazardous substances, including gas and oil tanks and any kind of firearms or ammunition.
Remove all pictures and other hanging items on the walls, and remove any antennas atop the vehicle.
If the RV will be shipped in subfreezing temperatures (for instance, on a cold cargo ship in the North Atlantic), prepare it as you would for winter storage, with water drained from plumbing systems and antifreeze in place.