When I write, I ask myself one question:
How do I want my next scene to look?
I have even played each character's part as if I'm a movie star. Of course, I do this in the privacy of my own home and when my family is out. On occasion, I will hold up my hands in the shape of a square and view the action the way I want my readers to view it.
My favorite compliment from reviewers are when they say to me: "Reading your chapter (or book) was like watching it play out on a movie scene." Success!
Why is it smart to do this?
Well, I think if you can't imagine your book on a movie screen, it's a bit dull, innit? The TV show THE OFFICE has something called "Talking Heads". It's where a character sits in front of the camera and talks to it. That's kinda what a character does when it's relating backstory or talks about themselves for paragraphs at a time. It can be really boring unless you have great writers like those who write for THE OFFICE. And if you are up to that quality of writing, please, put in lots of "talking head" bits. If not, imagine how it looks in your scene. Do you have lots of "talking head" scenes?
Next time you write a scene with thirty characters, act out the scene. Be all the characters. Remember all the lines. Move around. You'll be surprised how quickly you cut out the unnecessary characters - especially if the scene involves dancing or running a marathon.
The point is... write your book as you would like to see it filmed. If you could stand to watch your novel fourteen times while paying $40.00 for popcorn and a soda, you've got a winner!
If not, go back to the story board.