When viewing the car, always do it in daylight and take someone with you who really knows about cars. Take a long test drive on different road surfaces. DO NOT meet the seller at a location suggested by him unless it is his own address or his dealership. Get a credit history check done, its called an HPI check in the UK. This will ensure that the car has not been sold with outstanding finance on it. If it has and you buy it, you lose your money as the car still belongs to the finance company.