When you’re planning your screenplay make sure you only include the characters you need in order to tell your story. It may sound like an obvious statement but many writers make this mistake because they just don’t think about it. It can easily happen. You outline your story, flesh out the arc of your protagonist, clarify your theme and then dive into the script scene by scene. The problem arises because as you write event to event you simply introduce characters as they are required and before you know it you may have multiple voices all singing the same song.
Sometimes you may not even realize that this is a problem, let alone the problem with your screenplay and it’s usually left for others with a keen eye to point out. So if you are certain that each character you create is crucial to your story, just take a little time at the end of the first draft to read through with this task in mind and double-check you haven’t doubled up on essentially the same supporting character.
And watch out for “sounding-boards” – you know, the best friend who literally just waits around off-screen for the hero to enter frame and unload their hopes and fears. We all have them in our lives so I’m not saying get rid of them, just make sure you handle each “best friend” or “work colleague” in their own way so they have their own voice and own life so we, as an audience, don’t see that you’ve simply invented this guy or gal as a shoulder to cry on. Make us feel that they have their own lives and even their own character arcs. That’s right, just because their role in your mind is simply to be a sounding board, doesn’t mean you can’t develop their own journey.
Ask yourself, who is this person? Why are they in this scene? What do they contribute to the scene, protagonist/antagonist, plot and movie? Are they merely a sounding board for you or your central characters? If so, that’s not necessarily a bad thing so long as their dialogue and actions are handled deftly, but it is a bad thing if their dialogue is on the nose and expositional. And it’s a really bad thing if they take on the same basic role as another supporting character, i.e. propping up the lead.
If you do find a few characters that don’t really have their own unique voice and personality or even life outside of the movie then perhaps you should consider either rewriting their dialogue and role, cutting them, or combining them with another character who is more clearly defined.
The point to remember with movie writing is that you only have so much time to tell your story – so use it wisely. Don’t waste screen time on a character that is just there to plug a gap in an awkward silence or tell the audience the plot. Again, there are always exceptions but generally you need to be succinct in your writing and that means limiting the number of speaking parts to those that are absolutely necessary.