Movies are not books. Maybe you noticed this already.
In books, you have around 300 pages (or more, if your editor likes working long hours) to tell your story.
In a screenplay, you have 100 pages. That’s it. Not 120 pages, not even 116 pages. The average movie script is between 90-110 pages long. If it’s a low-budget script, I’m told you should aim for closer to 90. But no less. Less than 90 pages screams amateur.
Funny old world, isn’t it?
I personally have found that the best ideas to turn into screenplays are therefore the simplest ones. The ones you can riff off and create scenes from without much effort.
Imagine the story is like a single plant shoot. Your scenes are like the leaves coming off of this shoot. But if your shoot becomes twisty and crooked, your plant won’t grow straight. It might turn into an ugly plant. Of course it might also get eaten by bugs. But that’s another story…
So. The simplest stories work best.
“Liar Liar”. An attorney is forced to tell the truth for 24 hours.
“Jurassic Park”. What if we could clone dinosaurs?
That’s not to say you can’t have endless variations in scenes and subplots based on and expanding your story. “Annie Hall” is a great example of a very complex and varied script full of exquisite scenes that are based around quite a simple premise.
But when I overcomplicate my story spine, that’s when I get into trouble. And it can be frustrating trying to rewrite draft after draft until you iron out the kinks. If you ever do.
So when thinking about your screenplay idea, it pays to keep it simple.