I was a lot less naiive about buying a car this time around than I was when I was a recent college grad, but I still made mistakes.
Bruce Bueno de Mesquita, a political science professor and game theorist, outlined the procedure for getting the best price on a car. In his book
The Predictioneer's Game.
http://www.predictioneersgame.com/book
Call up 4 or 5 dealers in your area and ask them to make their best offer. According to Bueno de Mesquita, the dealer will insist you go in the dealership, and some will tell you to get lost if you refuse. But the ones who won't will try to make you the best offer so they can sell you a car. Get the best offer and then enter the dealership.
Once they get you inside the dealership, they will know your preferences, tastes, budget, and they can dictate the terms. Pay no attention to their feelings, because they're not paid to be your friend.
I still thought that I would visit different dealerships just as a courtesy. I went in to three different dealerships a total of six times. That just made the dealers have to drive to get you, and make you more obligated to buy. Bueno de mesquita's book was published in 2009. Apparently, it's 2015 and it's pretty much the norm to call around and get the best deal.
Still, I got a Prius for about $21,000. I put $10,000 down an got a five-year, interest-free loan.