Auditions foe The Miracle Worker, how will that go?

I am auditioning for the play based on the movie ( I think) called The Miracle Worker. It's about Helen Keller as a child. I want to audition for the part of Helen. Anyone ever been to an audition for this show? I mean, her character doesn't really have any lines or anything, so a monologue would be useless... anyone know how they choose an actress for a part like that? Any tips on how I can prepare?