That is something on its own that you have to Master. Dealing with customers and vendors back and forth all the time has taught me to get better and better at it. The problem is that there were a few bumps in the road that I wish I could have avoided, its one hell of steep learning curve. Slowly getting their and learning form everything is key.
The other I was in a heated meeting which great since it was back and forth over negotiations, and I was impressed with some people. It was experience that you cant gain from a book that I took to heart. Its kind of like memorizing a manual. Its also about the negotiation room you have, but the tactics were fantastic and the customer got cornered since he was given what he was asking for, so he was asked to commit. It was a difficult situation, and I have to say I learned a lot in that hour.