If you have an actor/actress in mind for your film, call the Writer’s Guild of America, and tell them you would like to have the contact information for the actor/actress you have in mind. You’re limited to 3 actors/actresses per call. Once you get the contact information, write up a small script about what you’re going to say, before you call. The fine point of getting through the gatekeeper, there will always be a gatekeeper, tell them how they can benefit by putting you through to the agent or the actor. Gatekeepers love to be the one who “discovers” the next great role for the actor/actress for whom they are working. 
One last thing, there are always going to be naysayers in the film business. Believe in your project. Believe in your passion. If you have a slam dunk story, you can get past having an A list actor/actress to launch your project. As for companies, simply keep in mind at all times that you’re bringing an intellectual property to them that can earn them millions of dollars.
I have learned that perseverance in the film business works. I know because I’ve been at it for 30 years. Don’t take no for answer.
