You wake up from chair, go to the kitchen, make a coffee, walk around the workstation looking that white immensity. You've probably heard something like this and, it can be real if are writing a book, but when you are a screenwriter, it's a little bit different.
When you start to write a new script you usually already know how the story begins and how it ends. Usually. there are several books on the subject and it is always good to read scripts to improve the technique. Of course, if the script is for an advertising film, that's one thing, if it's a movie plot, it's another. But anyway, first comes the idea. Yours or whoever created it.
Whenever I hear a story, a little movie plays in my head. I thought that everyone was the same, but I found out, not too long ago, that only 1/3 of people see things that way. So, when I put on my writer's shoes to work on a new script, every moment I create, I experience the feeling of emotion proposed for each scene as if I were acting in each of the characters. I can't help it, once an actor, always an actor. But it helps with the composition of each scene and the construction of each character.