During a meeting with a potential customer, a new salesperson leaves the room several times to make phone calls. Each time when she returns, she tells the customer she can't accept the terms they just negotiated. Exasperated by her apparent lack of authority, the customer ends the meeting abruptly.

As this scenario shows, your counterpart's constituents are bound to play a role in negotiations, whether you realize it or not. When the other side negotiates on behalf of an organization, his superiors and coworkers have a stake in the outcome. In more personal negotiations, his friends or family members may attempt to sway his choices.