I have sold about 6 cars in the last 3 years, and the best thing you can do is be honest. The other thing is make sure you know the market your selling to, the bulk of the cars I sold were modified cars, so i focused on listing on forum boards because thats where my audience shopped, I just sold my wifes 08 subaru in 6 days because I was able to price it below what the dealers in my area could sell it for. Dont be afraid to offer little things like offering to drop off the car