I find it helpful to choose a few inspiring or useful things to keep on hand during NaNo. I read the weekly pep talk that comes in the e-mail from NaNoWriMo. I keep "No Plot? No Problem!" close to hand. I have a few notecards I've tacked or taped up over the last few NaNos that carry inspirational messages, such as "Keep pushing. Never mind the yetis," a phrase adapted from a WriMoRadio podcast from a few years back. The computer monitor is crowned with three small plush animals who seem to look at me as if awaiting my next NaNo session, peering down expectantly when I come in to write.
It's handy that NaNoWriMo begins just after Halloween. Lots of tasty treats are available, generally for a sale price, since the stores don't want to keep the stuff around after the holiday is over. But it's a great opportunity to snag a bag or two of your favourite sugary treat, to be used to help push you along during NaNo. Use them as short-term rewards: "If I finish today's writing, I can have a chocolate." Keep a supply of your preferred caffeinated or writer-power-inducing beverage on hand.
On the subject of rewards, I proffer my own system: In the back of my novel notes book, I keep a running total of my word count from day to day. I also make sure I have some foil star stickers. Before NaNo starts, I decide on the scale of accomplishment. If my minimum total requirement is 1667 words, that gets no stars. Grade C. If I write 2000 words, I get a silver star. Grade B. And if I have a day where I write 2500 words, that gets a gold star: Grade A. At the end of the month, I tally up the number of stars and make what usually amounts to an arbitrary judgement as to what kind of prize I get for my accomplishment, regardless of whether I've won. I tie this system to my preferred writing program, TextRoom, which allows the setting of four levels of goals. I label them by grade, and I aim for an A.
Another tool I find invaluable is a random word/phrase generator. BigHugeLabs.com has a plot generator, and there are plenty of other random seed generators about on the Internet. I also have a game called Spinergy, which comes with a big spinner thing with word overlays. You spin it and it gives you three random words. When ideas run dry and you just need words, especially near the end of November, using a random word generator can help you squeak over the line, even if all you end up writing is a few thousand words about how an alien from the future enjoys cinnamon Pop-Tarts.