I'm auditioning for an independent film, does anyone have any tips?

There is an audition for an independent film this week and I really want to play the role. It's not the lead but I do play a character it is important to the storyline; she's a 17 year old girl who is troubled and depressed. I have never auditioned for anything other then plays and this is an open audition which is very very rare and it's also a great opportunity but I was wondering does anyone know exactly what Indy films are looking for in actors and what are somethings I can do to definitely get the part?