While I'm very careful to never use something my friend has shared in confidence, the people I love (and, yes, the people I'm not so fond of) definitely make their way into my writing. Especially in the early stages, when I'm still trying to figure out my characters.
I'll think of people I'm surrounded by now, or people I've known, and I'll jot down one-word (or sometimes a phrase) that comes to mind when I think of them:
Erin: The world revolves around me.
Lauren: Chameleon (someone who changes depending on who they're with)
Josie: Desperate to belong
Michael: Chip on his shoulder
(With the exception of Rachel, the names have been changed because I don't want to receive nasty emails from "Erin" "Lauren" "Josie" and so forth.)
After I've made a decent sized list (ten or fifteen or however many I'm in the mood for), I'll ask something like, "What actions make me describe Rachel as bold?" Usually I wind up with a list kinda like this:
- Moving to a foreign country even though she couldn't speak the language.
- How she always jumps in and plays with kids, even when she doesn't know them.
- Battled to catch the bouquet at my wedding
Then I'll look at my list and ask the question that really matters in the exercise - how do I apply this? Maybe my main character is a little reserved and could use a bold best friend to help draw her out. I'll think about Rachel a bit, think about my story and my characters, and brainstorm some possibilities:
- Best friend is always coming up with big plans for her future - like moving to South America despite only knowing English.
- Best friend loves kids and drives to a sketchy part of town to help tutor them.
The longer I brainstorm, the farther removed this character will become from my bold friend, Rachel.
Who is also quite funny. If memory serves correctly, nearby there was a middle-aged man sunbathing in his G-string (talk about bold!) so we had plenty to laugh about. Ah, Daytona...
So if all your characters are behaving the same as each other, don't be afraid to look at the people around you, examine what makes them different, and apply it to your story.
Let's throw some one-word descriptors out there. If you had to describe your best friend using one word (or a phrase, if you must) what would you say?