The business of screenwriting is all about writing and rewriting. The first step is writing a first draft. Then, step away from your script for at least a couple of days. Come back and read your screenplay all the way through. Read it again and take notes on anything that needs work. Are there any loose strings? Note any and all problems, from problems with the storyline to spelling and formatting mistakes.
Incorporate all of your changes.
Now it’s time to have someone new to your story have a look at your screenplay. You need to find someone who is unbiased and can be brutally honest with you. Give them a reasonable amount of time to review the script without questioning them about it. Once you get their feedback, remember that you don’t have to do anything with their feedback. Everyone will have something different to say. But, did any of the feedback resonate with you? Those are the issues you want to address in another rewrite.
By now your screenplay should be a tight read, interesting and well paced. Analyze each scene to make sure each moves the story along and contributes something to that story.
One of the trickiest parts of screenwriting for new writers is good dialogue. You’ll probably spend more time rewriting these parts of your script than anything else.
It’s not easy to make characters sound natural rather than stilted. Examine each block of dialogue. If it is longer than four lines on the page, you run the risk of boring the reader. Make sure your dialogue is not “on the nose.” The characters shouldn’t say exactly what they mean; their dialogue should be more calculating.
Imagine describing your story and characters to a friend, and then erasing all the character’s names in your script so that they wouldn’t immediately recognize who was speaking. Have you made the characters unique enough that your friend could guess who was speaking by their slang and the way they phrased their conversation?
Reread each block of dialogue and ask yourself if it sounds believable. Does the conversation sound like something you’d really hear on the street?
Listen to different types of conversations between different types of people. Spend time observing. You want your characters to sound real but if you really listen to people, you’ll notice that few of us speak in complete, formal sentences. Notice the differences in the ways people talk. Try to ignore the content while listening for slang, cadence and tone. Who is more dominant in the conversation and how do they convey that dominance? Imagine a friend or family member who’s something like your character speaking their words. If it works, keep it. If not, rewrite.
Remember that real people don’t have a conflict that they need to resolve in the next 90 minutes. Every word your characters speak must have a purpose. They should move the story forward as well as reveal subtle nuance of their character and backstory.
Examining your storyline and dialogue like this is a valuable step in polishing your screenplay.