Planning on buying a car any time soon? When I used to teach a personal finance class, I spent a good week on buying a car, since this is the single biggest purchase (outside of a house) most people ever make. Before you start down this road, make sure you spend some time educating yourself not just on the make and model you'll buy, but also on the car buying process.
The Motley Fool just ran a short piece on car-buying, titled Tips for Dealing With Car Salespeople . It's got a lot of useful tips, and a link to another article titled Confessions of a Former Car Salesman. I'd highly recommend both as a start.
Remember - car dealers are expert negotiators. So, before you go into the lion's den, educate yourself about negotiating tactics. I've mentioned this several times, but the single best book I've ever read on this topic is Roger Dawson's Secrets of Power Negotiating. It does a great job of not only giving specific strategies, but also of giving a good overview of the process of negotiating almost anything (from a car to your work assignments). At less than $15, it'll pay for itself many times over (and there's even an audiotape version).