5 Used-Car Red Flags
Came accross this article on Yahoo. Overall the advice is excellent.
“One of the most important aspects of a used car is its maintenance history. You want to make sure you’re buying a vehicle that has had routine oil changes and major mileage services. Always ask the seller, even if it’s a car dealership, for all service records.”
However, here is one recommendation that you will have a tough time following. Dealers sell 90% of the used cars sold in America, and it is VERY rare to find service records at a dealership. The original owner may have kept great records, but they may not have made all the way to the retailing dealer who is offering it for sale. A thorough pre-purchase inspection will show if a car has been well maintained or not (a point covered later in the article).
you’ll need to have someone else do a thorough inspection to make sure it’s in good working condition. A PPI, or Pre-Purchase Inspection, is performed by a neutral third party (such as a certified mechanic or automotive technician) and costs about $100 to $200.
Hallelujah! Absolutely true. 
See the rest of the article here: 5 Used-Car Red Flags