• Paperwork.

Have the seller provide as much documentation as possible, including registration and title documents, service receipts and proof of insurance.

• Odometer Rollbacks.

Digital odometers can be easier to tamper with, and the tampering harder to detect. Make sure the wear and tear on the inside and outside of the car matches what the mileage reading says.

• Flood Damage.

More than half of the cars damaged by floods get cleaned up and returned to the road.

• Curbstoners.

Illegal dealers posing as private sellers sell lots of cars either on the side of the road or through classified ads. Many of the cars have hidden problems and the seller typically disappears after the sale.

• Open Recalls.

Estimates are that 30 percent of all recalled cars go unfixed. Check for open recalls at www.carfax.com/recall and get more details about a specific recall at www.safercar.gov. Franchise dealers will fix open recalls at no cost.

• Certified Pre-Owned (CPO).

Perhaps the best value for many used-car shoppers, certified cars are the closest thing to new cars at used-car prices. Most manufacturer programs, such as those from Honda, GM and Toyota, include a rigorous mechanical inspection and a free Carfax Vehicle History Report with every CPO vehicle.

• Cars Sold Online.

Sites such as AutoTrader.com and Cars.com let you expand your search area and compare vehicles to find the best deal. Use discretion when buying from online classifieds and auction sites.

• Inspection.

An inspection by a mechanic or body shop and a Carfax Report is your best one-two punch to find the right used car and avoid costly hidden problems. Shop at reputable dealerships and say, "Show me the Carfax."