1) Get pre-approved for a loan if you are financing. Credit unions have rockin' rates on cars these days, usually as low as 1.xx% APR. Get approved and get a "buyers check". Then negotiate the deal with the dealership as a cash deal. If they can beat the terms of your pre approved buyers check, go for it. But they probably can't (or won't). This also removes their ability to sell you on a payment instead of a final price.
2) After you have decided which car to get, email all of the dealers within a reasonable driving distance (3-4 hours for me) and tell them what you are looking for and ask for an itemized, bottom line, out the door, drive out price. Be sure that they give you the drive out price that includes taxes, title, and any fees they want to charge. Also, don't give them your phone number. Keep the communication on your terms. The last thing you want is to be fielding calls before you have heard back from everybody. They hate this, BTW, and most of the web forms have the phone number as a required field. I just put the dealership number in.
3) Pick the top few (every time I've done this I've had 2 or 3 that are within $10 of each other for the exact same car). Email them back and let them know that you have other offers in that ballpark, and ask them for anything they can do to earn your business.

If you play your cards right, they will even deliver the car to your door. You give them the buyer check and they leave. No having them check with their manager. No sleazy finance guy trying to sell you on the undercoat protection and extended warranty. I bought one car a few years ago where I literally spoke with them on the phone for about 10 minutes, and the next day a nice retired guy showed up at my door and left 3 minutes later with a signed check.