From an exterior standpoint, your car needs to be protected. As such, store the vehicle inside or under cover whenever possible. Outdoor elements can wreak havoc on the paint and body condition of your car. If you don't have access to indoor storage, be sure to protect your car from adverse weather conditions as much as possible by routinely protecting it with a coat of wax. If you live in an area where highway personnel routinely salt the roads, you'll want to wash your car often paying special attention to the under carriage and seams where salt can accumulate and cause rust. In addition, it is extremely important to remove bird droppings from your car's finish. The acid will cause permanent blemishes to the finish.
If your vehicle has deep scratches or dings in the paint, be sure to have them repaired as soon as possible, especially if the underlying metal is visible. When exposed to the elements, bare metal can rust at a rapid pace. If left untreated, water will seep under the paint, causing it to lift off and the exposed areas will rust quickly, which will ultimately cause damage to a vehicle's body condition. What begins as a minor repair can lead to thousands of dollars in major body repairs as time goes by.
NADAguides.com offers a complete Car Detailing Information Center which outlines exactly what types of products to use when protecting your vehicle's exterior as well as how to use the specific products we've outlined. If you don't have the time to detail your vehicle yourself, you can always solicit the help of qualified, trained vehicle detail specialist to assist you.