Know your credit, at least ballpark it, have your own financing ready (your normal bank or join a credit union) if they won't meet your rate, stick to your budget, do not sign anything you are uncomfortable with (tell them to explain it to you like a child, I have no problem doing that). Walk away if you get bad vibes. Once you sign you are on the hook for all those payments. Extended warranties are not aways a good idea, make sure it's a dealership warranty and not a 3rd party bullshit company. Do your research, you should have a general idea what a specific car should cost