Edmunds.com has a very interesting, and information, article series under this title. Go to the site and then under the Tips & Advice link. One aspect not mentioned is what happens to your trade in. I have been told in states with a cooling-off period, your trade-in will be off the lot (sold somewhere) within hours of it being turned over to them. That way if you want to back out of the deal, you no longer can get your trade-in back through them. You might get back the trade-in value, but it would normally be less than the vehicle's actual street value.