Research the specific job being cast. For example, if the casting session is to find runway models, you will have to focus more on perfecting your walking style. If the job is for a magazine layout, focus more on your look and posing style.
Dress with the job in mind. If you are going to a casting call for a Valentine's Day lingerie commercial, you should dress in a way that emphasizes your attractiveness and desirability. For a photo shoot in which you would play the father of an all-American family, dress in comfortable clothes that any man would wear on a normal day.
Walk into the casting room with confidence. When you enter the room, grab their attention by striding with purpose and self-confidence. Remember, your audition begins the moment they call you into the room, and first impressions count. Wow them by walking in with good posture, making contact, and smiling.
Take on the personality the job requires. For example, if you are attending a casting call for a photo spread that showcases the male athletic form, project a masculine attitude in your stance and even in how you greet the people in the room. Casting agents and photographers will instantly imagine how you will look on a magazine cover or strutting down a runway, so help them to picture the correct image.
Answer all questions professionally but strive to inject your personality into the responses. Humor is a great icebreaker if warranted, but wait for the casting director to lead the conversation in that direction before you join in. Your goal is to create a comfort and ease that convinces the people in the room that you are someone with whom they want to spend time.