Edmunds is a great site! I learned soooo much about buying a new car there. They have such great info.
I would get the values before you go if you know what the car is you are interested in.
Dealerships always want to give you WAY less for your trade in, and then they sell it for the Highest book value.
Best of luck. Buying cars is not my favorite thing to do, but Edmunds sure helped me. I got a great deal on my new Accord.