2. Read the Dialogue Aloud
This is the first step a writer can take to determine if their character dialogue reads as common, ordinary, and interchangeable with other characters.
It starts in the writing process. Now, we know that most writers enjoy the writing environment of coffee shops, libraries, and other public places. While it can be embarrassing for some to talk to yourself as you read through the pages you’ve written, reading the dialogue aloud is a key first step. You can save the pages for a private verbal read in the comfort of your home or you can quietly speak the words under your breath in a public location.
The important factor is to add a little emotion to the performance. How do you want the character to say that line? Is it written in a way that is distinctive? Are the emotions evident within the dialogue? Do the moments in the script before and after that dialogue build to and deliver on those emotions?
Perform those words. You can do this yourself or you can go the extra mile and get friends together to read the script for you. You can even recruit actors to do a live read of your screenplay. This practice can further help you figure out if your characters are different enough from each other. You can ascertain if the dialogue works and is true to each character.
If the dialogue doesn’t play and it all sounds the same, then you know things need to be changed.