Hoe can I get the actors I want for my independent film?

I am working on my script for an independent film. A surreal, romantic comedy that pays tribute to one of my favorite filmmakers: P.T. Anderson. A hyperlink film that details New Yorkers and their love lives. I can't name a real celebrity for the protagonist but for the supporting roles I want: Shia LaBeouf, Debby Ryan, Victoria Justice, Leah Remini, Tyler James Williams, Lizzy Caplan, Johnny Depp, and Justin Berfield. I just need these actors, equiptment, distribution and a crew and I'm all set. What would be the first step in contacting them? What is the point of an indie film if you need a star and you can't sell it without one and also, financing and making contacts to get production rolling?