the key to selling a car or in fact anything is how it's advertised. you need to write down important details that people would want to know. I.e: what's done to it, any service history, show any receipts for work done, how it drives, what the engine, gearbox, brakes, suspension, body and interior is like. mention any imperfection it might have. basically you want the person reading it to know just about everything about the car before he sees it in person. you need to make the person reading it confident that what you are saying is genuine and honest.