B1 In Search of the Unknown p 4:
One player in the group should be designated as the leader or “ caller” for the party, while another one or two players can be selected as mappers (at least one is a mustl). Although individual players have the right to decide their own actions and relay them to the Dungeon Master as play progresses, the caller will be the one who gives the DM the details on the group’s course of action as they move around and explore (such instructions as “We’ll move slowly down this corridor to the east… ” or “We’ll break down this door while so-and-so covers our rear … ” are typical directions given by a caller to the DM). In the course of the adventure, the caller wlll naturally discuss the options available to the party with the rest of the adventurers, but it is he who the DM relies upon for the official instructions (although individual players can still pursue alternate courses of action at appropriate times if they Insist by telling the Dungeon Master). Once a caller (or any player) speaks and indicates an action Is being taken, it is begun - even if he quickly changes his mind (especially If he realizes he’s made a mistake or an error in judgment). Use your discretion in such cases.