7. Give yourself time and be ready to walk away

Dealers nearly always try to find ways to not honor those e-mailed price quotes you’ve received. Of course, they never say, “Sorry, we lied just to get you here!” But they don’t have to. They will say there’s a delivery charge because the color you want isn’t on the lot after all, or they’ll find a new excise tax to charge, or they’ll say you can’t get that car without $300 mud-flaps. That’s OK. It’s your cue to get up and leave. Exercise your right as a consumer to not tolerate this kind of misbehavior, knowing that four or five other dealers are ready to give you roughly the same deal. Even if you head to a dealer where the email price is slightly higher, you will pay less in the end by not dealing with a seller who is baiting-and-switching you this early on.

Note: You can’t take this walk-away step if you don’t have time, that’s why it’s important to avoid buying a car under duress. Don’t buy it the weekend before you are moving to a new home. Don’t buy it when your old clunker runs into a big repair bill. Don’t plan on getting home for an afternoon football game. Always believe that tomorrow is just as good a day to buy the car as today, and don’t believe when the seller claims, “this is a once-in-a-lifetime opportunity.”

On a related note, don’t car shop on an empty stomach! Eat a big meal, and know a dealer’s strategy can involve wearing you down so you fall for one of their traps along the way.

Remember: It’s OK to feel like a jerk. When you leave a dealership for bait-and-switching you, they will scream and/or cry as you walk out the door. They’ll tell you no one has ever accused them of cheating. That’s fine. In fact, it’s downright delightful. Many folks will say you haven’t really tried to buy a car until you’ve stormed out of a dealership for misleading you.

8. Bring a calculator, a spreadsheet or a friend

Speaking of misleading — I’ve purchased five new cars in my lifetime. During four of them, dealers made a massive mathematical error in their favor. This is not an accident. As good with numbers as I think I am, I didn’t catch most of these mistakes in my head. I caught them after I calculated the figures myself with an electronic aid.  You should always do the same, or at least bring a dispassionate third party (like a friend) who can do it for you.

9. It’s not over till it’s over

Many, many good deals go bad in the back room. That’s when the finance manager will try to convince you to take dealer financing rather than your own, or to buy an extended warranty, or undercoating, or some kind of anti-theft device. All of these things will be overpriced, and all of them can be purchased later. Remember rule #1 — isolate the transaction. Put another way: in a presentation on the car buying process that has a cult following, video game developer Rob Gruhl makes this point — “You wouldn’t stock up on candy at a movie theater.” Say, “No, no, no,” and hand over that check with only the out the door price on it.

10. Regret laws, sometimes

If you find you’ve been tricked into purchasing an extended warranty, many states have “regret laws” that give consumers five or 10 days to back out of that part of the deal, no questions asked. In Washington, for example, buyers need only drop off a letter at the dealer to get a refund for the warranty portion of the deal. (Also called “remorse laws” that entitle consumers to a cooling off period and a right of rescission, some states extend those rights to other contracts, such as health club agreements. They are aimed at industries that have a bad reputation for high-pressure sales.)

There is no such thing as a regret law for the actual car purchase, however.

Click here to become a fan of MSN Money on Facebook

More from Credit.com: