Don't ignore the interior. Clean leather and vinyl surfaces with good cleaners and restore their flexibility by finishing with a leather or vinyl treatment. Vacuum cloth seats and inspect for rips and tears. Vacuum carpeted floors thoroughly, and wipe all vinyl surfaces with a cleaner. Use chrome polish on all chrome areas, especially older cars' bumpers and custom wheels.
Some mags respond in an ugly way to the wrong cleaner, though.
Be sure you get a cleaner designed for your custom wheels. Throw away those empty washer fluid bottles, old oil cans, etc. Most car makers or accessory houses offer form-fitting trunk liners that will class up the trunk and cover previous abuses, discolored trunk carpeting and rust holes.