With theatre auditions comes the chance to perform a monologue. Unlike TV or film auditions, theatre auditions rarely have content provided for you to perform. So choose a good monologue that represents your talents but is also unique. Casting people hate overused monologues and will remember you better if your monologue sticks out. Make sure to know the time limit of your audition so you can plan your monologue better. Never be longer than asked. Avoid playing both characters in a monologue by speaking back and forth. Have someone read the other part, but place them behind the casting director so you can be seen better. Do not over announce what your monologue is. Just go on stage, introduce yourself, say what play your monologue is from and begin when the casting director is ready.
It is important to be comfortable at a theatre audition, so dress in clothes that give you an honest advantage. Don't wear anything too flashy, don't wear anything too dull.
Since you are preparing your own monologue, it is imperative that you have memorized it. Do not just pick a section of a play to audition with without reading the entire play. You should know your characters full story to fully portray one scene.
Before your theatre audition make sure to warm up your voice with vocal as well as breathing exercises. Arrive at least fifteen minutes early and be ready to go on at your given time. Bring a bottle of water with you. You can never guarantee the casting session will provide anything, so bring your own. Most important, have confidence and have fun. A casting agent will be able to tell when you are nervous, un-prepared, or scared. If you have practiced your monologue, are confident in your performance and have a good time performing your monologue, the casting agent will see this and hopefully add you to their production.