Auto Trader costs money, but it's probably better.
Get it detailed. Take LOTS of pictures. Of everything. Take a look at the CarMax website, see how they photograph stuff. Do your best to imitate that.
It's always a good idea to go to CarMax as suggested below, if nothing else you can get a quote and see what kind of price range you're looking at. If you can't find someone to beat their offer, you can sell it to them.