The CARFAX, that is. So you've had the salvage auto inspected by a qualified repair shop -- still, the inspection might not tell you anything about the car's past history as a wretched lemon. In addition to going on a thorough hunt for current damage, make sure you look into the car's past.
As a first step, consider a free Vehicle Identification Number (VIN) check at the National Insurance Crime Bureau. This will show you if a car has a salvage title, or if the car has been reported as stolen (but not recovered). You can usually find a car's VIN on the driver's side interior dash, where it can be seen through the windshield.