Select a play for production and thoroughly familiarize yourself with the roles that need to be cast. Jot down notes of age, gender and body types that have either been directly specified by the playwright (i.e., "Helen is a short, plump diva in her late 40's") or that spring into your own mind as you read the script.
Decide whether you want to have "open call" auditions or review actors by appointment only. In an "open call" audition (also referred to as "cattle calls"), anyone who wants to try out simply shows up on the day of audition. Appointment-only auditions are designed to limit the number of participants and are usually predicated on a certain level of experience and/or specific attributes (i.e., "Actors must be able to sing, dance and juggle bowling balls.").
Decide whether you want the actors to do cold (unrehearsed) readings from the actual script or to prepare 1-2 minute memorized monologues of their choice.
Schedule and announce through press releases, flyers, newsletters, and/or radio spots that you will be holding auditions in the theater or an audition hall. At the same time, determine what your rehearsal schedule (dates and hours) will be so that prospective performers will be aware of the time commitments expected of them when they come to try out for the play.
Decide in advance whether you are going to personally notify everyone of the audition results, post a cast list on the theater bulletin board, or only contact those who made the cut. Since actors often participate in multiple auditions, it's only fair to let them know by what date they may expect to hear from you if they have been cast.
Request that actors bring resumes and headshots to the audition. This will not only help you keep track of who was who, but also to narrow down the choices as you go by discreetly maintaining two stacks.
Explain the play and the roles being read for prior to the start of the audition process for those who are unfamiliar with the storyline.
Decide whether you want to ask the actors which roles they are the most (or least) interested in, or simply pair them up as you see fit.
Sit in the back row of the theater so that you can assess the actors' abilities to enunicate and to project. If you have an assistant, have the assistant sit in the front row with a tape recorder so that you can go back later and review the vocal variety each actor brings to the lines.
Allocate equal time for readings. Make notes throughout so that you can later jog your memory on the strengths and weaknesses of each actor.
Offer constructive criticism and, time permitting, allow actors to re-read for a particular part or to audition for a completely different role.
Stay open-minded throughout the audition process. Allow the actors to surprise you with what they can do when put to the test.
Pay close attention to how actors mingle with one another during breaks in the audition process since this can be an indication of how comfortable they will feel acting together. Someone who is snooty and stand-offish may be a great actor but could be a royal pain to try to direct.
Incorporate improvisational activities into the audition (i.e., having them play the characters in the script but in situations where they have to make up their own lines of dialogue). This is another good way to see how well they have grasped what the characters are all about and how fast they can think on their feet.
Schedule a call-back audition if you need the chance to see selected actors again before making your final decision.
Thank everyone for coming.
Make your casting decisions based on true talent, not on any pre-existing (or hoped-for) personal relationships.