If you want to get good at negotiation, you could go to your library and check out every book on the subject, then practice by doing low-risk negotiations like bartering for a car. (Be sure you read Getting to Yes and The McGraw-Hill 36 hour negotiation course. Oh, and “The Seven Habits of Highly Effective People” and anything by Dale Carnegie).
Or, if you want the super-cliff notes, you could read this article by Eric Sink.
Yeah, it’s that good.