First I have to say that I hardly dare call myself a "writer", so I'm basically just throwing in my two cents for the sake of the discussion.
I have two writing modes - relaxed and dedicated, in which I'll handle character creation very differently.
The "relaxed mode" is where I'll write hundred of pages a year around certain storylines I've used for... ugh, two decades already? Anyway, it is my brand of daydreaming. It is also where I work out some ideas that surface later in my second mode.
It's ok there for me not to define characters at the start, because I can just decide to rewrite certain key points... or be content with the fact I know they should have happened another way, and take it from there. Nobody's going to read it.
The "dedicated mode" is the one I need for sure in PBEM RPGs. (interactive writing, 1000-2000 words per post, a couple times a week. No three liners). Other people are going to read and hopefully enjoy the result of my efforts, sometimes depend on it, and they will also use my character to an extent. I need to establish a distinctive char that I can stay with in the long run, and remain consistent with it. Otherwise plenty of annoying side effects ensue for all.
The short story is, in "dedicated mode" I spend a lot of time defining a character at the top, after which I'm very careful about sticking with this biography and watching how they grow over time.
Now, about NaNo proper
I'm not a trained long distance runner and this is my first attempt at such a large format. In relaxed mode, the 50k would only be an extended outline needing a lot of rewrites. It would end up in the trash can with me discouraged once again... But I really mean to do this, so I switched to "dedicated".
I struggled for a week with my idea for the NaNo. My main char was rather bland and the story lacked an edge because of it. Last night I went working on "dedicated mode" and realized that this char embodies a concept that can't be revealed before the last third of the story. Doh! Meanwhile, the real main char, the one whose point of view will guide the reader, is the one I originally envisaged as a sidekick... (After that revelation, the outline just flowed from top to finish, yay!). Am I glad I found out now, because if I had just gone for my "relaxed mode" technique, I was toast. LOL
In any case, putting down all this in words helped me see a few things, among which that I have a couple strengths I should make good use of. I'm going to write bios (*) for these characters so the old training kicks in and I don't lose my way mid November!
I hope you'll find something interesting in all this, Tersa - I certainly thank you for starting this thread, and all that contributed. It helped
Athanasia
(*) Any lurker I dragged here who ever heard me say I'd most definitely not write another bio this year had better stop sniggering NOW. *eg*