How you deal with potential buyers can make or break the deal.
Answer the buyer's initial telephone questions. If they're keen to view, arrange a time when they can visit; don't take the car to them.
Be polite, helpful and honest. Answer the buyer's questions and demonstrate how things work if asked to. Let the buyer take his time.
Emphasise plus points and ownership advantages - good fuel economy, reliability etc - but don't be pushy or oversell the car. Be honest about significant faults that the buyer should notice anyway.
Offer a test drive provided your own or the buyer's insurance covers this. Again, allow plenty of time - half an hour is reasonable. Agree to a car inspection if the buyer requests one.
Be reasonable but firm when negotiating. The buyer may open with a low offer; state clearly the minimum you're prepared to accept. Let the buyer walk away if your target price and his best offer are too far apart.