You can write it however you want! Some people prefer writing random scenes in any order. Others have it meticulously in order and seperated into chapters. I've recently begun to write it in just one long thing, without breaking it into chapters.

Short answer: no rules! Just words.

thanks to everyone who came out to the kickoff party! it was a great success c:

We'll be having weekly write-ins through the rest of november, and we're aiming to have informal, short, drop-by-if-you're-free-and-in-the-area write-ins as well, so make sure to join our facebook group or email to be added to the mailing list to get updates on times and locations! and if you're still debating whether to start or not, it's only day 3; you're only 3333 words behind and you have a whole weekend to catch up! go check out the site: www.nanowrimo.org

Thought I'd post an update on the createspace offer:

It appears that createspace has come back with something similar to last year's offer for nanowrimo winners, according to the sponsorship page:

"Five free paperback copies of a finished book for NaNoWriMo winners

CreateSpace is proud to support NaNoWriMo participants. We invite you to explore easy and rewarding independent publishing; take advantage of free services or choose from our everyday low priced professional service offerings. Get started here. In addition, NaNoWriMo winners can get 5 Free paperback copies of their finished book; details will be posted at CreateSpace after November 1." http://www.nanowrimo.org/en/offers
https://www.createspace.com/nanowrimo

edit: all you have to pay for is shipping.
source: http://www.nanowrimo.org/en/forums/s.../threads/91549

edit edit: unfortunately, there appears to be a catch:
"4) The offer is only good on books published through CreateSpace. They have a variety of different distribution channels, ranging from being available widely on Amazon.com and Amazon’s European websites to private options."

this may potentially limit you from selling your book to a publishing company if you're assigned a createspace ISBN, but I'm not really sure if that's true or if there are other implications from this restriction. I mean, if you never plan to publish your novel with a big time publishing company, by all means, this is a great offer.