Scripts with vague main characters get set down by studio or agency readers by p.10, if not sooner. Enhance your characters by giving them 4 traits. Of the 4, have 1 of them contrast with the others.
Example, your main character might be ambitious, arrogant and uncaring about others. But his/her 4th trait might be that he/she is secretly afraid that his/her world is meaningless.
Each word & action by that character then comes out of one of those traits. More than four is too confusing. Fewer & s/he will feel “flat.”
Keep in mind the difference between a trait and a characteristic. A characteristic might be that s/he is a gourmet chef or gifted pianist. But a trait would be that your character has a fragile sense of self which manifests as always needing to be the center of attention. Traits take your reader inside your character and how they view and feel about the world.
A characteristic is an action your character does. A trait is why s/he does it.
Do this exercise for each of your key characters and watch your script come to life and your characters come off the page.
Have a great writing day!
3 days ago