Depending on where you live, check for rust around the wheel wells. Check the under carriage too.
Look at or test everything. By this i mean cupholders, windows, mirrors, spare tire. Check it all so there are no minor annoying surprises.
Ask if it has been in any accidents. Check the seams in the engine bay. It's pretty obvious when a car has been repaired from an accident.
Push down on the body over each wheel. If it "bounces" around quite a bit, the shock is done.
If you havent found any problems yet and youre going for a test drive accelerate fast, brake hard (not to be confused with bagging the fuck out of the car), wiggle the steering wheel back and forth to put stress on the suspension. Listen for odd sounds.
Take it for a mechanical inspection if you haven't found any problems and you are serious about buying it. The dealership is usually a decent bet.