Know which one you are and respect the rules of your genre. They're just protecting their jobs. If your character hasn't changed by the end of the story, you fail. After he changes, he dons the cowboy hat, signifying the New Billy. Hollywood, being star-driven, favors screenplays with strong, castable roles.
Agents are close to impossible to get.
Frankly, Hollywood doesn't give a damn about your theme. If your screenplay doesn't get a reader emotionally hooked, you can be as sure of getting rejected as you are to find a t-shirt shop on Hollywood Boulevard. Then you're ready for the Three P's, according to Richard Krevolin. For those living outside the L.A.-cosm, patience is even more of a prerequisite. A comfort offered by Krevolin is that Hollywood has as many people who will look at writers from outside L.A. as it has people who flat out refuse.