Face time, unguarded moments, the counterpart's religion and the 'crazy' check.
Chris Voss's framework, from Never Split the Difference, pp. 175 to 200.
Face time
Meet in person.
Unguarded moments
Start, end, interruptions.
Religion
Their worldview.
Crazy check
Bad information, constraints, other interests.
From chapter: CHAPTER 10 | FIND THE BLACK SWAN, pp. 175–200
Opening on the 1981 Rochester bank siege where William Griffin killed a hostage on deadline, Voss introduces the Black Swan, a piece of unknown unknown information that changes a negotiation. He argues every side has at least three. Black Swans multiply leverage, which comes in three kinds, positive, negative and normative, and he shows how learning the counterpart's 'religion' settled the Dwight Watson tractor standoff in Washington. When a counterpart looks crazy, they are usually ill-informed, constrained or pursuing other interests. The chapter closes with how to find Black Swans, through face time and unguarded moments, and with the argument that fear of conflict is the real enemy.