Beware the deadly pronoun: he, she, they, especially the infamous they and the power-gilded we.  Pronouns can send you into a quagmire of misunderstanding.  Every single day, it seems, I say to someone, "Too many pronouns."  During a negotiation, force your counterpart to use specific nouns and proper names.  This preventive measure avoids a great deal of miscommunication.

- Michael C. Donaldson, Negotiation for Dummies

You need to set your goals and define your limits before the actual negotiation begins.  After you know your goals and limits, you can decide on your opening offer.  Your goals and limits carry you right to the end of the negotiation, enabling you to decide when to close a deal and when to walk away.  The very process of setting limits gives you power in a negotiation, because the process forces you to focus on what else you will do if you fail to reach an agreement.  I call that your or else.

-Michael C. Donaldson, Negotiating for Dummies