Industry publications like Automotive News are great sources. If these sources report your target car has seen slow sales lately, you've got extra leverage. The cars on the lot don't even belong to the dealer. Since you can't ever really know the dealer's bottom line, go for the best price you can get, and negotiate from a base of knowledge. The dealer knows the option prices cold, and so should you.
Options give sales people a bewildering number of combinations to impact price.
Take time out during negotiations to check the dealer's numbers against your own. Take a notepad, pen, and a calculator for this task. The sooner you pay off your loan, the more you save on the total price of the car. What to say to the dealer when the heat is on. Vince Dandini is the kind of guy car dealers hate to see coming.