There are three very important rules in regard to creating value in a negotiation. The first concerns the meaning of value itself, which is expressed as Value = Benefit - Cost. We've all, of course, heard about sales processes that are supposed to add value but hardly ever succeed in creating real, measurable business value. A strategic negotiation process does succeed though, because it enables you to add "hard" value (value you can measure) rather than "soft" value. If you can't put a potential trade through the equation above, you're not creating value.
The second rule is Never concede - always trade. If you simply concede on an item during a negotiation, you are eliminating the possibility of creating value because value is created by trading items that have differing importance to the two sides in a business negotiation.
The third rule is Never negotiate one thing by itself. If you negotiate one item at a time, you will soon find that you don't have any other items with which to trade. If you can't trade, you can't create value.
Listen to this short video interview of Brian J. Dietmeyer, Think! Inc. President and CEO on price negotiations.