If you are bad at negotiating, bring the number of all the car dealers in the area who are selling the car you want. Also, bring a cell phone. When they quote you a price, say "thank you" and start calling around. Tell the other dealers what price you've just been offered. This way, you get them to do the bargianing for you.
This is a sure-fire way to P.O. the dealership and get yourself booted. Trust me, I've seen it. As shady as you
think the dealerships are, this is just low class.
Now, as someone who has sold cars (Hondas in fact), the best advice I can give you is to do as much research as you can and have a price in mind BEFORE you go to the dealership. The worst thing you can do is to ask them "what's your best price?". Don't do that. Ideally, you should hit them with a price. Even better still, phrase it in a way that you don't actually state the price of the car. If you want to buy the car for 15k, you want $k for your trade-in, and you can put down $2k, tell them you'll buy the car RIGHT NOW if you can finance $10k, put 2k down with your trade-in. You might not get the price you want but at least you have a good start point. If you start battling for the price of the car right off the bat, you've lost.
Some other semi-insider advice:
If your trade-in is more than 4-5 years old or has more than 50k miles, they don't even have to look at it. Almost everything goes to auction. Dealerships will give you the "fair" rating straight out of the Blue Book. Sometimes you have very little negotiating power in this department. All the more reason to use the method I discussed above. Give them an offer as a package deal.
Good credit is a very strong bargaining chip. Most people don't realize it but the interest rate CAN BE NEGOTIATED. The dealership is under no legal obligation to give you the best rate possible. In fact, most of their money is made with loans (aka the "back end"). If you have good credit, you should be able to get rates around 3-4%, sometimes lower.
Newspaper ads: If you see a deal in a paper that looks too good to be true, it probably is. The print ads usually have some very strict criteria with them. Often times the prices listed are for cars with standard transmission or even without AC. The ads are to get you into the dealership. They dealership does NOT want to sell you the ad cars AT ALL.
Also, don't go into the dealership with the belief that they are trying to screw you. Don't be combative. Be firm but be polite. Remember, it's not personal. You can get up and walk out any time you want (even though they'll try to stop you).
Oh, and for the record, Hondas are awesome. They are some of the best cars on the road and better than some cars much more expensive. Their reliability is second-to-none. I'd take a Honda over Toyota in a heartbeat. Hondas are a lot more fun to drive too.