Buying a used car tips. Get a thorough inspection—Have a mechanic inspect the car. Pay for this service, money you invest up front may save you dollars down the road. Ask for a written estimate of the costs to repair any problems the mechanic finds, and use that estimate as a bargaining chip when you make your offer for the car. Have an auto diagnostic test done. Use National Automotive Dealers Association (NADA) Official Used Car Guide, monthly Kelley Blue Book (www.kbb.com), or Edmund's (www.edmunds.com) to estimate a car's resale value.