No matter who you buy from, always look over the vehicle thoroughly and take it to a mechanic for a complete inspection. Dress in old clothes and give the car a good going-over. You can learn a great deal just by using your eyes, ears, and nose.
Take along a friend for help. Do your inspection in broad daylight on a dry day. Floodlighted lots can make cars look shiny and can hide body defects. The car should be parked on a level surface and shouldn't have been driven for at least an hour before your inspection.
Body condition. Check each body panel and the roof, looking for scratches, dents, and rust. Examine the lines of the fenders and doors. Misaligned panels or large gaps can indicate either sloppy assembly at the factory or shoddy repair. The paint color and finish should be the same on every body panel.
If you think a dent may have been patched with body filler, put a small magnet on it; it won't stick to an area with body filler. If other parts of the car have been repainted, there may be signs of "overspray," or paint adhering to the rubber seals around the hood and trunk lid.
Minor cosmetic flaws and light scratches are no cause for concern, but rust is. Check the outer body for blistered paint or rust. Also inspect the wheel wells, rocker panels (the sheet metal beneath the doors), and the bottoms of the doors. Bring a flashlight for looking inside the wheel wells for rust or corrosion.
Open and close each door, the hood, and the trunk. Gently lift and let go of each door, particularly the driver's door. If the door seems loose on its hinges, the car has seen hard or long use. Inspect any rubber seal for tearing or rot.
Glass. Look carefully at the windshield and windows to make sure there are no cracks or large pocked areas. A small stone chip may not be cause for alarm, though you should bring it up as a bargaining point in negotiations. But cracks in the windshield will worsen and lead to a costly repair.
Suspension. Walk around the car to see if it's standing level. Bounce each corner up and down. If the shock absorbers are in good shape, the car should rebound just once; it shouldn't keep moving up and down. Grab the top of each front tire and tug it back and forth. If you feel play in it or hear a clunking or ticking sound, the wheel bearings or suspension joints may be shot.
Lights and lenses. Have a friend confirm that all lights are working. Make sure all light lenses and reflectors are intact and not cracked, fogged with moisture, or missing.
Tires. You can tell a lot from the tires. A car with less than, say, 20,000 miles on the odometer should probably still have its original tires. Be wary of a low-mileage car with new tires; the vehicle's odometer may have been rolled back. Also check that all four tires are the same. Any different tires may show that they have been replaced.
Tread wear should be even across the width of the tread and the same on the left and right sides of the car. Ask if the tires have been regularly rotated. If not, the wear is usually more severe on the drive wheels.
Aggressive drivers tend to put heavy wear on the outside shoulder of the front tires, at the edge of the sidewall. Assume that the car has been driven hard if that area is badly worn relative to the rest of the tire.
Tires that have been driven while overinflated tend to wear more in the middle than on the sides. Chronically underinflated tires show more wear on the sides. Cupped tires, those that are worn unevenly along the tread's circumference, may be a sign of a problem with the steering, suspension, or brakes.
Tires must have at least 1/16 inch of tread to be legal. Check the tread depth either with a tread-depth tool (available at auto-parts stores) or a quarter. Insert the quarter into the tread groove, with Washington's head down. If you can see the top of his head, the tire should be replaced.
Examine the sidewalls for scuffing, cracks, or bulges, and look on the edge of each rim for dents or cracks. And be sure to check that the spare is in good shape and that the proper jack and lug wrench are present.