Remember these words next time you are haggling at the dealership. By David Muhlbaum, Senior Online Editor Originally published August 21, 2015 Most of us know that there are certain things you’re supposed to do and not do when buying a car, but it can still be a struggle to put those principles into words. For the most part, car-buying remains a tough negotiation. And you’re at a disadvantage: The sales representative does deals every day, and you don’t. He knows what to say; you don’t.See Also: 12 Best Used Cars to Buy Now Here are three situations you’re likely to face in your next car-buying adventure -- and our suggested responses, which will keep the conversation going the way you want and lead to the best price you can get. 'Thanks, I may consider your trade-in offer' Dealerships like trade-ins. It gets them inventory for their used car lot on the cheap. So don't be surprised if you get offered money for whatever you drove to the dealership. The offer might even sound surprisingly good. But don't bite quite yet. Your answer? "Thanks, I may consider your trade-in offer. But that's separate from how we're going to price the new car." The point is this: It's hard enough to keep track of one price as you're negotiating. Once you've gotten close to final on the new buy, you can entertain the trade-in bid. If you've done your research, you know what your car is worth and can take it or leave it. Advertisement 'Let me see the invoice, please' It's hard to buy a car without a lot of extra fees. But not all fees are created equal. When you last bought a shirt, did the store charge you to take it off the hanger? So, don't pay money for silly things like vehicle prep fees for pulling shipping plastic off your new ride and making sure it has oil in it. When the dealer tells you "everyone pays these", your line is, "Let me see the invoice, please." Legitimate fees are listed there. 'No, thank you' Finally, you can expect to be offered all kinds of stuff once you hit the dealership's Finance and Insurance office, from window etching to protection plans for your key fobs. The line you're going to need to use here the most is simply, "No, thank you." Mud flaps, rust-proofing and paint sealants make the dealer a lot of money, but you can often get these for less elsewhere—assuming you want them in the first place. Look at a catalog such as AutoSport for accessories, or check your local detailing shop for paint sealant or fabric treatments. If you later decide you just really have to have those chrome running boards, you can always come back to the dealer. Here are three more smart things to say at the car dealership.