Bargaining for Advantage -- the book by G. Richard Shell
Shell repeatedly cites Influence, as well he should, given that he spends the bulk of the book applying Cialdini's insights to the bargaining process. Unfortunately, Shell does not have the same talent for rationalizing subject matter, so one has to sift through the book (well worth the read) and build its ideas into a mental model, as the one provided has omissions and does not lend itself to visualization.
Refactoring Shell, the bargaining process has three elements:
Shell rehashes a bunch of Cialdini in his explication of The Dark Arts, however Shell leaves the Information side of mapping out your opponents needs curiously unexplored. On page 85, he describes a $1.6E10 negotiation for the sale of Core States Financial to First Union: Core's CEO had cold feet, not because he thought Core wasn't getting enough $$$, but rather because he felt he was betraying the communities (knowing that First was probably going to consolidate/liquidate some branches). So, First created a $1E8 charitable foundation to help those communities, and the deal got done.
Identifying and Classifying the various psychological needs would help immensely, as satisfying those needs will often cost less than increasing your primary offer. I think many people operate under the illusion that we negotiate based on one metric (say price/value), while our decision process actually takes into account many other variables.