Documentaries are stories about real life. Your subjects will have their own thoughts so your documentary script needs to be flexible, especially at the beginning of your project. However, in order to focus the content of your filming you will need a shooting script at the beginning and an editing script by the end of your project. Here's how you can write your documentary's script.
The First Script or Shooting Script
Have your documentary topic completely researched. Before you start shooting, you need to have an idea about what your story will be. As with dramatic films, there needs to be interesting characters, conflicts and plots. Unlike dramatic films, these should occur naturally, without directing the people in your documentary.
Write down an outline of what you think your documentary will be about. This outline needs to include the characters, their conflict and how you imagine their conflict will be resolved. Your documentary will change as you begin shooting, so right now all you need is a vague outline.
Create a list of questions that you want to ask your characters. These questions will help to develop the characters and investigate their conflict. As you shoot, your characters' answers will provide you the meat of your documentary.
Begin shooting, now that your shooting script is done. Make sure you cover all of the questions you had, but be ready to take your documentary in a different direction if a new, better conflict arises. As your conflict changes, keep editing you shooting script.
Second Script or Post-Shoot Script
Complete all of your filming, and start your post-shoot script. The purpose of this script is to help you or your editor know exactly what to do to complete the project.
Choose the scenes that you shot that best develop your characters, conflicts and plot. Write an outline of the scenes that you intend to use in your final documentary.
Write, word-for-word, the script for your documentary. This means that you will write the dialogue of your characters as well as the narrator's dialogue. Remember, your script needs to be complete so that another person who edits your documentary will cut the dialogue just as you envisioned.