Spend a coupla hundred on a nice clean and shine jobbie if ya don't or can't do a good one yerself...then change the oil ,and all the lil things that need to be in tip top shape....then BE HONEST...if the floors rusted and the tranny on it's last legs....scrap it.......set a reasonable price (see ads in AutoTrader etc for YOUR equivalent vehicle) and allow a few hundred OFF in the negotiating.....good luck..........