Communications: be careful about using the phone, e-mail, and other nonvisual communication vehicles. A lack of facial expressions, vocal intonation, and other cues can result in a negotiation breakdown. Constantly reiterate your interest in the other side's concerns and your determination to find a mutually satisfactory resolution.
Personalities: be conscious of aspects of your personality such of your own needs and interpersonal style as well as the other person's personality; these factors will play a key role and understanding yourself will be an important factor
Your own personality and style: how much you trust the person; how free with your emotions; how much you want to conceal or reveal;
Physical space: sometimes where the negotiation takes place can be important; are we negotiating in a space we are uncomfortable and other is comfortable?
Past interaction: if there is a history of conflict resolution with this person, think about how this history might affect the upcoming negotiation
Time pressure: Think about whether time pressure will affect the negotiation and whether you need to try to change this variable?
Subjective utilities: be aware that people place very different values on elements of a negotiation. For example, in negotiating for a job, you may place a high value on location and relatively lower on salary; it is important to be aware of your subjective utilities and try to ascertain the other person's subjective utilities; it is difficult to know in advance or even during the negotiation what a particular outcome will mean to the other party. Finding out what is "valued" is one of the key parts of negotiation.