One way to write any story is to think of your story world. George Lucas didn’t just write a screenplay about a Death Star. Instead he created a world for his story to fit in. “Avatar” wasn’t just a science fiction movie, but a world of alien animals and spiritual natives. Even “Fargo” isn’t just a dark comedy but a world of Fargo and Minnesota where people talk a certain way and look a certain way.
By creating a whole world, you create a much richer story telling experience. “Jurassic Park” wasn’t just about dinosaurs running amok but about people creating genetically modified dinosaurs and then losing control of them. This allowed multiple sequels that basically told the same story about humans losing control of their dinosaurs and facing the disaster that occurs.
In your own screenplay, think about the world that your story inhabits. No story world is dull and ordinary. “Beverly Hills Cop” contrasted the gritty world of Detroit with the far more glamorous world of Beverly Hills. “Miss Congeniality” took us into the world of beauty pageants. “The Hateful Eight” takes us into the Wild West filled with bounty hunters and gunslingers. “Silence of the Lambs” took us into the FBI training academy and into the mind of a serial killer.
The point is that the world your story takes place in must be unique, original, and a character in itself. The kooky way people talk and look in “Fargo” is just as memorable as the story. The war soldiers behave in “Fury” or “Saving Private Ryan” is just as important as their goal itself.
So imagine a world for your story to inhabit. If you make that world different and memorable somehow, you’ll also create the option for sequels if your original story proves successful.