tip 1: don't look like as if you really want the car. act cool
tip 2: when they ask what price range that you want to be in, dont tell em.
tip 3: intimidate them. mean mug em
tip 4: dont buy into that " thats the lowest i can go" pressure em
tip 5: dont work with the total price, work with the monthly payments. for
example: if the car payment is at 450 @ 5 years term. talk them down to 350 or lower. Most used dealership will do what it takes to make a sale.
tip 6: make sure that you don't get screwed over by the interest, If youre getting a great price for the car but youre paying it at %29.999 interest youre losing a lot of money in the long run. which goes back to tip 5. DONT negotiate the over price negotiate the monthly payments!! Since your monthly payment usually includes the interest.
tip 7: bring paper, pencil, and a calculator. MATH IS YOUR BEST FRIEND
tip 8: do a hundred mile search and compare the prices and mileage of each car. if you find a cheaper car, youll might be able to save even more!!!
tip 9: if you have transportation, you might be able to find a much better deal at within 200miles.
tip 10: Salesmen are only there for your money, they arent helping you at all.

Haggle is your best friend. ask them to throw in some free goodies if they wont bring the price down. i got a free Volkswagen t-shirt, keychain, mug and a emergency kit after haggle the price down to an amazing deal.
Goodluck and best wishes! Don't rush if you feel like that you can do better with the price or that you can find a better deal.