I'm always looking for new things to talk about on this blog; if you go back through old posts, you can probably tell when I was having trouble coming up with stuff. Anyway, I joined Stumble Upon so that I could find more blog content. And this is one of the pages it took me to, the other day:
12 Character Writing Tips for Fiction Writers
Never mind that "writing" and "writers" are in the same title only a few words apart. And I haven't explored the associated site, but it looks like there may be other resources worth checking out, as well.
I'd caution against revealing all the backstory at once, and please don't describe your character physically upon first appearance, if it doesn't make sense to. (For example, Katniss in The Hunger Games refers to her "long, dark braid" but it's a first-person narrative and unless she's suddenly sprouted a long, dark braid, it's just her HAIR to her.) I'd also caution against inventing kooky patterns of speech for characters (and that includes pretty much any dialect, which is just painful to read -- I'm looking at you, Karen Miller and Mercedes Lackey). Still, some characters can speak more formally (there's a guy like this in the Belgariad, I think, though I forget his name), some can curse, etc.
That's not to say that you shouldn't think about these things. In fact, I'd highly advise developing a complex and interconnected world view, history, and profile for each character. Just don't infodump it all at once. Make sure the details are consistent and drop them in when it adds to the story. Don't do it for the sake of filler.