Make sure that the expiration date stamped on the plastic has not passed and it has never been used in a crash. You can’t be sure about the history of a used seat unless you got it from a friend or relative. You will need the detailed instruction booklet (it can be ordered from the manufacturer if it is missing) to check that the seat has all of its parts and to find out how to use it correctly. Check for possible damage, such as cracks in the plastic, frayed straps, stiff buckles or harness adjusters. If the safety seat passes all of these criteria, you still need to check for possible recalls.