The retail installment sales contract
At a dealership, the car purchase and the loan usually live in one contract. It lists the price, your down payment and trade-in, every fee and add-on, and the loan terms. Before you sign, match it line by line against the out-the-door price you agreed to. Anything you didn't agree to comes out.
The cost disclosure
Federal law requires the contract to show the loan's cost in a standard box: the APR, the finance charge (total interest and fees in dollars), the amount financed, and the total of payments. Compare the APR against the pre-approval you brought from your bank or credit union. If the dealer's number is higher, ask why.
The used-car window sticker (Buyers Guide)
Every used car at a dealer must have this sticker. If it says "As is — no dealer warranty," that means repairs are your problem the moment you drive off. Keep the sticker; it's part of your contract.
Add-on contracts (the ones to slow down on)
GAP coverage pays the difference between what you owe and what insurance pays if the car is totaled. Optional — and your own insurance company may sell it for less. Extended warranties and service contracts are optional too, and can repeat coverage you already have. If you're told any add-on is "required for the loan," ask them to show you where the contract says so.
Title and registration papers
The dealer usually files these and you drive on temporary tags until the real ones come. Buying from a private person? The title transfer at the DMV is your job, usually with a deadline.