An assistant director (AD) keeps a production running smoothly, particularly in the director's absence. A person in this position is responsible for being at every rehearsal and meeting and for filling in for the director when his schedule requires him to be in two places at once, such as at a rehearsal with the cast and at a production meeting with the technical crew. A limited amount of authority comes with the responsibility in this position, but in all things, the assistant director must answer to the director.
Before the production is cast (that is, before actors are hired), the assistant director must read through the script and become familiar with its technical needs as well as the director's vision. The AD may help research items from the time period of the play or other details to make the production more realistic. Through meetings with the production staff, such as the producer and the technical director, the AD assists the director to make sure all administrative duties are taken care of, including cast and crew contracts, insurance contracts and venue rental fees and schedules, if applicable. During auditions, the AD provides a second set of eyes and ears so the director can discuss particular actors with the AD and make appropriate casting decisions.
During rehearsals, the AD and the stage manager often share the duties of making sure all of the director's decisions and notes are written down. While the stage manager generally takes notes regarding the physical needs of the play, such as where the actors move and stand, the AD will often note the broader needs, such as additional staff or meeting space needed. The AD may also take actors who are not in a scene off into a separate space to rehearse, guiding the actors toward the director's vision. Alongside the stage manager, the assistant director is responsible for making sure all needs get communicated to the appropriate people, including acting notes, technical notes and schedules.
Once the play has opened, the assistant director may not have any official duties, as the show is officially handed over to the stage manager at that point. However, many productions use stage managers and assistant directors almost interchangeably, so the AD may be asked or required to take notes on missed lines or assist with backstage cues to ensure actors enter at appropriate times.
Although not generally a part of the AD's official duties, the assistant director in a theatre production often takes care of the little things that make the director's life easier, such as getting her coffee, tea, water or food and following up on e-mail communications the director does not have time for. Preparing the stage for rehearsals and helping clean up afterward may also fall to the AD. The AD, like all cast and crew members, may be asked to assist with promotional efforts, such as distributing posters and fliers for the show.