National Novel Writing Month starts at 12:01 AM, November 1st, wherever you are. (Just follow your local time, and you'll be fine.)
I'll be wrapping up my outline after the Halloween festivities this evening, and tomorrow, I'll roar through my first 1,667 words (at least) to make sure I'm off to a good start and to create some nice momentum for myself.
To present and future Wrimos, here's a great resource from Mahalo: How to Win at NaNoWriMo. Under Step 4, it is stressed how important it is to start (with a brief mention of my post—thanks, Nicole!):
The main reason people fail at NaNoWriMo, say participants, is that they didn't start. If you don't write anything on November 1, you're already behind on your word count. Kristin Gorski gives a great scenario of what happens if you don't start on November 1.