So you're trying to write, trying to find a voice for your characters.
An easy trick is to print photos. Cast all of your characters. Print photos of a friend or family member that is inspiring your character, or maybe it's a celebrity? Movie stars have a "voice" and scripts are often revised to support their brand. Imagine the difference of writing a character for Jack Black vrs. Angelina Jolie. You'd focus the dialogue more, you're also have freedom to play.
Granted all of these "casting" choices probably will change before the time the final film hits the big screen but it can be helpful to a writer to find a voice for the characters and hear them speak from the page while writing.
Grabbing photos is easy, you can go on Google and do a search. Almost all working actors have a headshot of some sort online. You can print fairly nice 4x6 headshots of your entire cast with most office printers and hang them on the wall in your workspace. Label them with your character's names and boom!
...you have a cast.
