Your analysis should identify the relevant legal and business issues. The emotional component of my perception must not be overlooked. Know yours and know theirs. You will most certainly miss a golden opportunity or you will react caustically to statement born of frustration unless you anticipate both your reactions and your opponent's reactions to the topics and the sequencing of topics. Kindness at a critical juncture establishes the trust upon which the agreement is built.
Objective criteria allow the discussion to progress.
Build your opponent a golden bridge to retreat across. When you both have a problem, a solution is not a zero sum game. This is the most difficult task. A negotiator should identify the topics of discussion as well as the sequence of discussions. Everyone has a preferred negotiation style .