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.