Just How Short?
The length of your short is entirely up to you, but if you're planning on filming it yourself and submitting it to festivals, shorter might be better. For festivals, I've seen it recommended that your short be no more than 10 minutes long. A shorter short film eats up less time in the schedule, making it an optimal choice for festivals who want to play as many shorts as they can.
Keep Things Simple
We all want our stories to be compelling and something no one's ever seen before. Writers sometimes needlessly overcomplicate their stories in an attempt to achieve that. Your short film is probably not the time to write from multiple points of view, have various storylines, or bounce from plot twist to plot twist. This isn't a hard and fast rule; you should be experimental and try new things in your writing! Keep in mind that a more straightforward story is one that an audience can more easily engage with and relate to.
A strong concept can help a short film to stand out. A short with a strong concept is easy to pitch, it's easy for readers and viewers to remember, and it's easy for other people to talk about!
Tell a Complete Story
While short films can be used as proof of concept for feature-length ideas, your short still needs to be able to stand on its own and tell a specific story. There should always be a clear beginning, middle, and end. Your main character should have goals and encounter obstacles that they must overcome. Like a feature-length script, acts are essential, but the number of scenes and sequences will change to fit the shorter length.
We've all heard that film is a visual medium, and we should always write with that in mind. This is incredibly important for your short film! If all you have is 10 minutes to tell your story, you need the visuals to stand out and make a significant impact. Leave a lasting impression on your reader or viewer.
Tell Only What We Need to Know
In a feature, you have more time to color the story and supply moments that will give a taste of character, setting, or relationships between people. In short, you need to boil things down to the most critical moments of the story. There's no room for fluff moments. Cut to the heart of things, and get into and out of a scene as quickly as possible.
When writing a short film script, the most important thing to keep in mind is to be concise, be visual, and tell a full story. Hopefully, these tips spring to mind and help you the next time you find yourself writing a short. Happy writing!