1. internet research
2. see if their website has a "call for special internet price/promos"
3. figure out EXACTLY how much you are willing to pay before you go in
4. hopefully be MMM enough to have cash: unless you're getting 0% financing we're gonna facepunch you
5. as someone said, go in the day before the end of the month: 30th, 31st
6. be polite, but firm
7. get the GM of the dealership involved, and sell HIM: "Mr. Jones, I'm local, so if I'm happy, all of my local friends are going to hear your name. I have cash and can have my bank wire it to you in seconds. Treat me right and I won't buy just this car, I'll buy ALL of my cars from you." (he has no idea this might very well be your last car if you're mmm)
8. be prepared to walk. Grimace, thank them for their time, say "I guess I should have checked (their biggest local-ish competitor name) before coming here." Walk.
You will get a call/email within a day to see if you did buy at the other dealership. Say you think they are meeting your price of xxx. "Can you beat it, because I'm tired of playing around: I am buying a car today."
Say "oh, that's the other dealer on line 2: can your GM email me your best price, because otherwise I'm just going there now".
Good luck.
Also...it's all an equation. So if you have something popular/pristine to trade that they want (or already have a customer waiting for) they can sometimes make enough on the back end or even trade-in that might bring your numbers down. Although usually you'll get more for your current ride on craigslist.
The opposite is true: if you want a TRD PRO today you will pay MSRP (west coast) because there are so few on the ground and no one has or will give them up to another dealer.
A good negotiator can actually beat the Costco club price.