Meet my MC, Derek.
Okay, so it’s not really my main character. This is an actor.
Why would I post a picture of him when I said I was introducing you to my main character and telling you how I get inside his head?
Because this is how I do it:
1- Pick an actor who would be great at portraying my MC in the movie version. (It started with choosing him because he was a physical match for my MC.)
2- Imagine said actor (it helps if you have seen the actor’s work a lot so you’re familiar with their intonations and inflections) saying the lines of dialogue or acting out the scene you’re writing.
3- Fix anything that makes you react in all the wrong ways.
There you have it! This worked really well with Lodestar for me. There was a scene that I wrote which I instantly broke out into hysterics over upon imagining him saying one line. All it took was changing one little line of dialogue and I found the scene to be more in character. And that change was prompted by the small and simple act of imagining the scene like it played on a movie screen.