http://www.carfax.com/vin.cfx - If you want to make sure the used car you are eyeing is a good buy, try conducting a VIN number lookup. Performing a VIN search is one way to know the history of the used car you are interested in. When you receive the VIN history, you can decide if it is a worthy investment or not. The VIN can be found on the car or in the car insurance papers.