Although this book it out of print, it has a wonderful and easy to use "checklist" to prep up for a negotiation. It is a great follow-on read to Getting to Yes! and talks heavily about the process of negotiation.

Corporate negotiation is a process like all other business strategies. In today's challenging and ever-changing business environment, it is imperative to understand negotiations from the perspective of both the buyer and the seller. In Strategic Negotiation, Dietmeyer and Kaplan use a research-based approach to negotiation that assists sales professionals in reaching their own business goals, while ensuring that their customers meet budget and professional objectives as well-going beyond win-win to achieve true, measurable business value for all parties at the negotiating table. The authors use their own strategic, four-step negotiation process to teach sales professionals how to attain quantifiable value in their dealings: