Car dealers try to present the transaction as "one thing" - purchase price, trade in, financing, warranty. They figure out which one of those things you are most sensitive to, and then give you a good deal on that part, making up the difference by not giving you a good deal on the other parts.

Even if you want to buy a car, with a trade in, and finance it, and you want an extended warranty (sometimes those can be okay, that's a whole other story that I am happy to talk about if anyone is interested) -- you should still go in and only talk about one thing at a time.

Zeroth step: If anything gives you pause anywhere along this process, walk. There's other cars, other dealers, other salespeople. Always be ready to stand up and leave, and don't just make empty threats.

First is to find a vehicle that suits your needs - something you would buy. Then get an "out the door" price on that vehicle. That price is going to include all the fees and taxes and registration, not just the purchase price of the vehicle.

Only after you have that in hand do you move to the next thing, and that would be trade-in. If you want any offer on a trade in vehicle, that vehicle will need to be at the dealer with you for them to inspect it. They're already eye-fucking the car you drove in, from the moment you came on the lot. In order to get that trade in offer, you will need to hand over your keys. Yes, your car is now a hostage to keep you in the dealership. "While they're checking your trade, why don't we talk about financing, warranty, accessories, pre-paid maintenance?" No. One thing at a time. You will refuse to talk about any other aspect of this transaction until your trade has been evaluated and a trade in price settled on. You may need to demand your own car back so that you can leave.

That's done, you have agreed on a trade in price (or you do not have a trade in), now you can talk about financing. If you intend to self finance, skip this step. Even if you do not intend to self finance, you should have done some research on what kind of rates you could get from a bank or credit union, otherwise you have no way of knowing whether what the finance office has to offer is competitive.

The finance office will also be the place where extended warranty is offered. In short, if the warranty offered is an exclusive warranty (covers everything except what's on a particular list), it might be worth it to you to get. An inclusive warranty "only covers what's on this list," and those are universally bad. Adding the warranty to the financing might affect your interest rate, but it shouldn't be by very much, if at all.

Make sure that you're satisfied with the condition of the car. Something doesn't work? Unsightly door dings? Ask if the dealer can take care of those. Maybe they will, maybe they won't, but you don't know until you ask. Paintless dent repair probably costs the dealer $25 per ding for their vendor to come do it, maybe they'll pass that along to you at cost to get the deal done. Anything the dealer promises to fix, they will write you a "We Owe" for. If it's not on paper, it's not going to happen.

All done, right? Nope. Now they will draw up the official paperwork for the transaction. Check every single line item on that sales contract to make sure they all match what you were promised. What's this extra fee for? Why is the price of the extended warranty $400 more than what you said? How come I'm being charged for dealer-added pinstripes when I never agreed to that? Remember the Zeroth Step? Be ready to walk. You've been in the dealer for hours now, and they're banking on you just being tired of going through this and wanting it to be over. Even if everything is correct, you can still walk at this point. Don't let your emotions get in the way.

Now you can sign the contract and drive off in your car.