Keep the gas tank filled under a quarter of a tank. It reduces the weight of the car, and transporters will appreciate that.
Secure or remove any loose parts or specialty items from your car such as ground effects, spoilers, or fog lights. If you have wide mirrors fold them back. Lower remove, or retract the antennae if possible.
Always ship convertibles with the top secured properly. Seal any holes or open seams in the top to prevent moisture damage. If you cannot raise the top, consider closed container shipping.
Have a charged and relatively new battery, properly inflated tires, and make sure all fluids are at adequate levels. If you have ANY leaks from your car be sure to tell transporter so he can position you car properly. Cars leaking oil and especially brake or transmission fluid should NEVER be on the top of a two deck open trailer. This is to prevent leaks onto the paint of vehicles below.
Prepare a careful list of any operational problems or steps necessary to start, stop, or drive your vehicle on or off the trailer.
Make a Thorough Vehicle Inspection: In order to ensure any claims of vehicle damage are accurate and enforceable, make a complete report of any pre-existing damage your vehicle may have. Dated pictures can be a very effective in making claims on damage.