I think I understand. For as long as I've been writing, I've been told to "just write." Turn off the internal editor and get it on paper. I've tried, but my brain still gets in the way. Leave it to a screenwriter to get it through to me. Robert McKee talks about "writing from the inside out" in his book, "Story." For a novelist, it's second nature to write from the viewpoint of one character and stay in that character's head. For the screenwriter, it's a little more difficult. McKee actually includes a scene from "Chinatown," where the hero is confronting his suspect. Now, before every single line, there is a short paragraph explaining what's going on in that character's head. Essentially, the notes portion of the scene is what you'd use in a novel.
For the novelist, it needs to go a step further. As I write, I should be including everything that's going on in my POV character's head as well as the other characters in the scene. The difference will come in the editing, where I cut all the stuff the POV character won't know, and even quite a bit of what he does know. What I'll get is a more realistic scene. Allow me, if you'll be so kind, to attempt an example.
Tracy knew that Jack killed his brother, but she couldn't let him know that she knew, or she'd be dead, too. She struggled to keep her face smooth, the muscles in her cheeks from twitching. "Jack," she said, "what brings you here today?" He's knows, oh Lord, he knows. Stay calm, Tracy. After all, you were in a relationship with this man once, he can read me like a book.
Jack studied her eyes. She's nervous about something. Could she possible suspect that I killed my brother? No way, she's too stupid. She could barely balance her checkbook. "Just wanted to say hi, Tracy. We're still friends, aren't we?" And I've got to get that computer file off your desktop. I never should have saved it there. Idiot! What was I thinking? Just play it cool. You don't need her blabbing to her friends that you were pulling files off her computer. But how to get her out of the room. "I was hoping to borrow that old belt sander you got from your dad." She'll never buy it.
OH NO. He's trying to get me in the basement. Blah blah blah.
So there's a really bad portion of a scene. I've gotten into both character's heads, which doesn't work so well any more in modern fiction. Now, stay with me, I'm brainstorming this idea as I go. But if I write a rough draft like this, I've got choices to make, good ones. After typing out ten pages of this nonsense, I have to decide which POV to go with. I don't have to do it before writing the scene, as I normally would. See what I'm getting at? I can make the choice, depending on who can provide the most tension, who generates the most internal conflict. I think that's great. I may try this tonight. Of course, I'll end up writing something like what I have above and getting maybe three lines of dialogue and two sentences of internal conflict. It's like mining for gold after you've created a mountain of dirt.