(MONEY Magazine) – With prices for used cars up 8.9% this year vs. 2.3% for new ones, now is a great time to sell your old auto -- especially if you have your eye on a 1994 model. If you sell it yourself, moreover, you may raise 15% to 20% more than you'd get from a dealer. Some tips: -- Spruce it up. Have your car detailed (cleaned down to the last fender groove) for about $150 at a local auto detailing shop. And fill the tires with two or three extra pounds of pressure to make it handle more nimbly. These moves, plus proof of good care (such as a maintenance log with receipts), can add $1,200 to your car's value, says Ashly Knapp of Seattle-based AutoAdvisor, a consulting and buyer's service. -- Price it right. Find the going rate for your model in the National Automobile Dealers Association's Official Used Car Guide ($12.95; 800-248-6232). Then adjust it up or down depending on prices of comparable cars in local ads and your car's condition. -- Write a straightforward ad. Shell out about $60 to $200 for a week of classifieds, but keep the ads easy to read. Don't advertise over holiday weekends, like Christmas or New Year's. Nobody shops then.