The most important character in your screenplay is your protagonist: your hero. It's her story. We hope and fear for her. She' the interesting somebody who wants something badly and is having trouble getting it. Without your hero, there is no story. But when creating that unforgettable protagonist, you must know the whole package – the entire iceberg – which is no easy task, but follow these Ten Key Rules and you'll sculpt a hero that breaks the mold.
1. You must create an interesting protagonist, one that your audience will want to watch, hope, and fear for.
2. We don’t have to feel sympathetic toward him/her (although it is a great help), but we must at the very least feel empathy.
3. We love to see characters acting bravely, so it is not only what the character is trying to accomplish that makes us cheer for him or her, but it’s the lengths he/she is willing to go to get it. Make sure the lengths are far. We want a journey.
4. Know your main character. His/her dreams, wants, desires must be there on page one. Ask how we identify with, relate to, or are fascinated with him/her.
5. A central character cannot exist without conflict. Make sure you have enough obstacles (internal and external) that your character must face.
6. Your main character must have a weakness (hopefully many). They are often oblivious of these weaknesses, or in denial, or constantly trying to hide from themselves.
7. Attack your main character at his/her weakest spot, and he/she will show things about him/herself that he/she doesn’t want to reveal.
8. Your main character should not be aware of the full dimensions of the theme at the beginning of the story, but he/she will learn.
9. Think of your main character unfavorably. This will make them believable and more human.
10. Change. Make sure your characters learn as they go. How does he change? What does she learn? How is he/she becoming someone different.