Don't get trapped into making concessions because you have already invested a lot of time and effort in a negotiation. Always consider your original goals and be prepared to back out and break of negotiations. Do not assume that your opponent thinks exactly like you, and at the same time do not think they are your complete opposite. The truth lies somewhere in the middle. Do not reply in a haste.
Patience pays off.
If a negotiation is complex, do not rely on your memory. Try to use objective criteria to evaluate offers. Negotiating Agreement Without Giving In , Penguin New York, 1984. No , Bantam Books, New York, 1993. The InterNeg Group.