Political science professor and game theorist Bruce Buenoa de Mesquita wrote a book published in 2009 called The Predictioneer's Game in which he advised that you call 4 or 5 different dealerships and ask them to make the best offer. Some dealers will tell you to get lost, but some won't. Once they get you inside the dealership, they control the game.

Apparently, it's 2015 and getting 4 or 5 different offers before setting foot in a dealership is the norm.