In an interview with Marc Maron, Matthew McConaughey described looking for “a launchpad line” to access a character:
That line is not an attitude. It’s a part of his constitution. It’s an encyclopedia on that guy and that belief. It’s like The Wolf of Wall Street. The way I was able to riff on that was one of the lines that was written is when he tells Jordan Bellfort, the Leonardo DiCaprio character, the secret to stock broking is cocaine and hookers. I’m like, ‘What?! Who’s that guy?” There’s a book on that guy, if that’s truly his perspective and he really means that.
He goes to say:
“Then the rap stats. I can write that song, hundreds of thousands of pages, based on that one-liner. Unpack that, deconstruct that guy.”
I love this approach, both to acting and writing–finding one line that offers a window into who a character is. As Maya Angelou says, “When someone shows you who they are, believe them the first time.”