I am a four time Nano-vet, and a three time winner. Here's a few suggestions, grouped by topic.
1) Sit down and take a long look at your schedule. The rule of thumb of 1667 words a day is fine if you write the minimum every day. If you have things scheduled that will interfere, like exams or doctor's appointments, make a note and subtract those days from your Nano month. Let's say you have things to do and weddings to attend and you really only have 25 days in November. You need to write a minumum of 2000 words a day to finish.
2) Take your vitamins. Starting now, until Nano begins, eat healthy, exercise, get enough sleep. Take care of you. The better shape you are in when it starts the better your chances of not falling ill.
3) Activate your support network. Talk about Nano now so there are people rooting for you. Hating to actually say to a friend 'No, I blew off writing today' could be just enough to keep you pushing.
4) Figure out now what you will eat, and lay in supplies. Include reward foods or writer kibble or whatever you can make and freeze. If you drink coffee or some obscure Greek soda, buy it now.
Preparation: Your Home/Computer
1) Bust loose and clean. The cleaner it is before you start, the less of a pit it will devolve into when you get lost in the wilds of your novel.
2) Get your writing area ready. Clean it up and lay in your reference books and music and whatever else you think you'll need.
3)The time to figure out which software you'll use is now. Get RoughDraft or Word or whatever and take some time to learn how to use it.
4) De-frag your drive, clean up your files. If you have been putting off computer repeairs or upgrades, do them now. Nothing sucks like losing writing time to being on hold to order a new drive.
5) Determine how you'll back up your novel writing now. Thumb drive? Email it to a buddy? Write to a disk every night? Pick something,get used to using the method and stick to it. Because I lied above, and realizing the drive just died and your novel just went pffft sucks even worse than ordering a drive.
6) Lay in your office supplies. Me, I have to have index cards for my Nano (I can explain how I use them to keep on track if anyone's interested).
Preparation: Your Novel
I like to do a lot of prep work. I write up character ideas, I do interviews or I free-write from the character's point of view. None of this goes in my novel, but having done it gives me a handle on the story.
There's a load of good ideas on novel prep at the Nanowrimo site. I know folks who love the Snowflake method. I use my index cards.
Prepare for success. For every daily goal I hit I treat myself to something. For milestones like each 5K of words I give myself a gold star. No, really, I buy them and I put them on my daily index card. I've been known,as the local ML, to give out gold stars at the meetups.
Any other Nano-veterans want to chime in with their suggestions?