I had a friend of mine go backstage after a Broadway show and hand the security person her resume, saying she wanted to shadow the Stage Manager, and to please have them contact her. The Stage Manager of Wicked did contact her and she did shadow. However, her resume was good. I don't know if they'll contact everyone who attempts that. Off-Broadway might work too, if you don't mind walking in the stage door un-invited it is worth a shot.