I just finished reading Orson Scott Card's how-to write book "Characters and Viewpoint." What a killer manual! This is exactly the kind of thing I want to read when I'm looking for tips and advice. Card doesn't waste any time, just gets down to the straight goods.
What's really interesting about this book is how simple a lot of the advice is. The stuff I found the most helpful were the passages on things that ought to be obvious: for example, how to flesh characters out with habits, networks of relationships, and different kinds of--even conflicting--motivations. Card constantly reminded me of the little things that make characters authentic and likeable.
That's not to say he ignores the big stuff, either; his examination of different types of narrators and points of view was also incredibly illuminating. All in all, this is a really solid book with a lot of helpful advice; and, clocking in at less than two hundred pages, its a fast and very worthwhile read!