L.F.
I did all of my negotiation for my new minivan over e-mail. I got some e-mailed quotes from local dealers through cars.com and edmunds.com.
My best results came through my bank. If you bank through USAA (military), they offer pre-negotiated car prices. The pre-negotiated rate for my Honda Odyssey was $100 below invoice. I contacted a few dealers and asked them if they could beat that price, and they did. So I ended up buying my car for about $260 below invoice. I hate negotiating, and I was prepared to pay up to $500 above invoice, so I was pretty happy with the outcome.