7 ways to get bottom dollar for a used car

In the Internet age, photos make up the single most important feature of any used-car ad, and that's where a lot of people drop the ball, Kovach says.

One mistake she sees is sellers not using their allotment of photos for online ads. Buyers want to get a complete picture of a used car's look and condition before they commit their time and energy to look at it in person. If they don't see high-quality photos, they may not even give your car a second chance, Kovach says.

She recommends including multiple shots of the exterior and interior, and detailed shots of the odometer, the tires and the interior of the trunk to give potential buyers a clear picture of the car's condition.

"Really, you just cannot take enough pictures of the inside of your car," Kovach says. "You want to create a virtual walk-around for the people viewing your ad."