Take a classic story such as Cain and Abel or Romeo and Juliet and see how putting those characters into your screenplay or novel gives you a sudden insight. Does your story “pop” more when your character is more aggressive like Cain or a victim like Abel? Is your story more effective if your lead is the one calling up to the balcony or looking down at her love?
Now take a moment to consider your own favorite stories and throw one of those characters into your work. This technique can work for both heroes and villains, or love interests or buddies. The heart of drama is relationships.
Good luck and happy writing.