If you insist on car shopping yourself and not paying a professional to look at the car before you buy it. These tips will help you get started in the right direction. First I look for things like:
Body damage: look for over spray in the wheel wells, under the hood, on the radiator or condenser. Most used cars that get touched up get done fast and cheap.
The body shop will tend to not be careful taping things up to avoid over spray. A good thing to look for is the factory stickers in the door jambs and under the hood.
If they are painted over or missing most likely the car was repaired and painted. Another sign of paint work is tape lines in the door and trunk jams.
Almost all cars will have a tire pressure label inside the driver’s door. If it is missing the car was most likely hit. Body shops try to make the most out of the little money the insurance companies pay them and little details like stickers will not get replaced.
Another good place to look is the door latches in the door jamb. They will often have over spray on them if the door was painted and not taped up.