Here are some additional tips that I've heard.
* Run a carfax report and make sure the title hasn't changed hands like a hot potato.
* If it has higher than average mileage, check the condition of the rubber pad on the brake pedal. It might help indicate if they were highway or city miles.
* For body work, check if the paint has been disturbed around the bolts fastening the body parts.
If you don't know the vehicle's history, then I should hope you're getting a good deal.