How would a normal everyday person go about auditioning for a musical theatre role?
I don’t have better information than clawofiron– listen to her. But I would like to add that, first, you should stop thinking of yourself as a “normal, everyday, average person” with “nothing uniquely special.” First, that doesn’t mean anything. Second, it’s not going to help you in any way. I’m not saying you should have delusions of grandeur, but if you think of yourself as nothing special, and tell other people that you’re nothing special, they’re going to go, OK, bye. Figure out what you have to offer. Why should someone cast you and not somebody else? Also, broaden your focus. Rather than needing to get into this one, specific, professional production, look for acting opportunities everywhere.