Scripting writing is a form of writing.
It’s all dialogue. Everything written is something a person will say. So writing scripts means you can bend and even break the rules of grammar for the sake of the listener.
Keep it short. It has to be read. People have to breathe. They can’t speak aloud a really long sentence. Sentence fragments are acceptable. Single words are also OK.
When writing a script, imagine how a person will speak the words. You can say them as you write to get a better feel of this. If you have problems reading it aloud, then something needs to be changed.
Simple words. Simple sentences. Break complex ideas up.
If you know what the words will be spoken over, then you can match your writing to fit the images.
Depending on how involved you will be with the video production, you can include directions in the script. Don’t get detailed. Let the director do his job too.
When writing a script try to budget 110 to 150 words per minute. If it is a complex subject, go slower.