Hi writers, I've written and self-published two books, both of which were pretty well-received (by the few people who consumed them). I'm also an avid reader, and although I'm not as voracious as some are, I typically read at least one to two dozen books a year or so. My point in stating these facts is that while I feel pretty confident about my ability to judge a book based on its merits and my personal reaction to its structure, and even though I've written a couple of novels myself, I'm still not very confident about writing interesting, three-dimensional characters. I'll leave plot structuring alone (another area where I feel very weak) because that's a subject for an entirely different thread.
Anyhow, I was thinking about the characters in the book I'm currently working on, Year One by Nora Roberts. Without turning this into a review of that story, I felt it started out very promising, but many of the characters have turned out to be extremely one-dimensional/thinly written (to me, at least).
For those of you who have a lot of experience with writing, or who feel good character writing is one of their strengths, I would love to read any advice or thoughts you can offer on the following points/questions:
How do you write characters who are truly multi-dimensional, and what makes the difference between a poorly written and well-written character?
Why can some authors write relatively "one-dimensional" characters who are still so interesting? I think a good example would be Randall Flagg from the Stephen King universe, who is just a flat-out evil bastard without a lot of moral depth to his personality, yet he still manages to be an extremely compelling villain.
What are the biggest pitfalls to avoid when writing characters, and how do you avoid Gary Stu/Mary Sue syndrome, etc.?