To prepare a car for shipping, clean it inside and out, remove all personal belongings, disable the alarm system, and secure any loose parts. Take photos of the car and note any pre-existing damage. Empty the gas tank to 1/4 or 1/8 full, remove the battery or disconnect the negative terminal, and remove any custom accessories. Finally, check with the shipping company for any additional requirements or recommendations, and make sure to have all necessary paperwork and insurance in order.