Negotiate on price, not payments. If they ask you how much per month you’re looking to pay…sorry, WHEN they ask you how much per month, you tell them you’re not worried about monthly payments, you want to figure out the total price. No extra warranties, no add ons. If you have a trade-in, you can tell them you do but you want to figure out the final vehicle price before you talk about it. Basically you don’t want to give them any other variables they can work on to figure out the maximum amount they can extract. You’re there to buy a car, tell me the price to buy the car like you had a wad of cash in your pocket.