This document discusses common assumptions in negotiation and their likely impact. It provides actions that can be taken to challenge restrictive assumptions and maximize the benefits of supportive assumptions. Some key assumptions discussed include: the purpose of negotiation is to win at any cost, which risks damaging relationships; open communication allows understanding of different perspectives; negotiation does not need to be adversarial as win-win solutions are possible; and a counterpart's first offer is not necessarily their best or final offer. The document recommends considering the interests of both parties, building rapport, and taking a collaborative, long-term approach to find mutually beneficial outcomes.