I've heard about using personality categorizing systems to help in fleshing out characters . I think it can be a good tool, *after* you have done some basic character development. One of the systems I like (maybe just because it's cool) is the Enneagram. A couple years ago I had a little side business where I sold used books online. I learned a lot about what sells (and keeps on selling) and even though I'm no longer doing that business, my personal library got much bigger during the 2 years it was actually making a profit.
Two books that I decided to keep and not sell because they were so interesting were books on the Enneagram. They were fascinating! I showed them to my extended family at Thanksgiving over a year ago and several people ended up taking the tests and reading up to see what it had to say about us. After my brother borrowed the books for a while I kind of forgot about them until I read a blog by Scott Rhoads over on the Utah Children's Writers blog.
Here are the nine basic personality types:
Type 1: The Reformer. The rational, idealistic type.
Type 2: The Helper. The caring, nurturing type.
Type 3: The Motivator. The adaptable, success-oriented type.
Type 4: The Artist. The intuitive, reserved type.
Type 5: The Thinker. The perceptive, cerebral type.
Type 6: The Skeptic. The committed, security-oriented type.
Type 7: The Generalist. The enthusiastic, productive type.
Type 8: The Leader. The powerful, aggressive type.
Type 9: The Peacemaker. The easygoing, accommodating type.
The really fun part is when you mix your main motivational type (not your only) with "wings" - or types on either side of your main type. So a Type 1 Reformer with a Type 2 Helper wing will be motivated and react differently than a Type 1 Reformer with a Type 9 Peacemaker wing. And the books I have go into detail also about the types at their worst, at their best, when stressed, in relationships, and what's good and what's hard about being that type.
Since Scott Rhoads said it so well (and that means I don't have to) I'll refer you to his blog about using the Enneagram Personality System to Create Characters. You can go take a peek after you finish this post (of course). :)
I did the online quiz for my main character last week and it nailed her pretty good, but if I had to flip through the book and pick a type I don't know that I would have gotten what the quiz did, mostly because I didn't know her well enough yet. After reading in more detail about her personality (and she was split evenly between two of the types) I feel like I'm really getting to know her. The great thing is that now I know some weaknesses I hadn't realized she had. And I can imagine how other personality types would automatically conflict or complement her.
Anyway, I just thought I'd share. And if you're curious, I'm a Type 3--the goal-oriented list maker who takes work even on vacation and must, above all, be competent but sometimes turns into an uptight work-a-holic who needs to be smacked upside the head and reminded to chill. Yeah, that's me.