These include what are your and the other parties' objectives, what are both parties' concerns, what is the past history of the parties, is any party bringing any preconceived notions to the negotiation.
You also need to consider the bottom line point that you will not go past, and what is your alternative course of action if a successful outcome is not reached.
Remember after the negotiation ends, you will still have a relationship with the other party. It's a fine balance between getting what everyone needs and maintaining a healthy business relationship.
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