Doing your research is the most important thing. I bought a truck last December. It is amazing how little some of the salespeople know about the vehicles they sell. You would think that they would at least do their homework and know everything about the vehicles and the incentives and rebates that their company offers, but many of them don't.
Edmonds.com is a great site for researching the vehicle you want. I learned that advertising costs vary from area to area and affect the cost of the vehicle, in other words, the vehicle price is going to be higher than Edmonds' pricing. I went through the Costco car buying program and got my truck for $500 over dealer invoice. That, and 0 percent financing that I got, made it a really good deal for me. This purchase was a very pleasant experience and far different from most of my vehicle purchases. The salesman really knew his stuff and literally went the extra mile for me in several areas. I wanted trailering mirrors on my truck, and didn't realize my truck did not have them. In his office he had a new pair of mirrors that had been taken off another truck, which he sold to me at cost. When they went to mount the mirrors, they found out the mirrors were not the right ones....so they put the correct new mirrors on and ate the price difference. I wanted running boards on the truck, and my saleman volunteered to apply for some unheard of rebate available to certain professional people. While I was willing to pay whatever, I got their best running boards for $500 thanks to the big rebate he found. The guy loves his job and really has an understanding of people. Too bad he only sells Chevys, because I'd buy my next Toyota from him in a flash.