Tips on auditioning for Marion in the Music Man?

I'm auditioning for the Music Man Jr. soon and I really, really want to be cast as Marion. I need some tips on how I can make sure I stand out, channel her but still be myself, and be the best candidate. I have a pretty good voice, but its nothing next to a lot of people and I've also been acting for a long time. I'm 14 by the way. Thanks so much!