Even though National Novel Writing Month (NaNoWriMo) may seem like a purely mental game, it's also intensely physical. Your body has to be well maintained to make sure your mind is at peak effectiveness. Junk food, though convenient, is not helpful. Beyond just not having much energy, you can even get sick from the stress you put on your body. Be sure to eat healthy to have the energy to power through. If you can't eat healthy, at least EAT regularly as you will burn up energy while writing.
2. Get regular exercise!
Go to the gym. Go for a run or ride your bike. Take walks. Every little bit helps to maximize the ability of your body for the rigours of NaNoWriMo.
3. Take regular breaks!
Staring at a computer screen for hours at a time will affect your eyes. If you work in a job during the day that requires you to look at a screen for long periods of time the risk of tiredness and headaches is even more pronounced. Adopt a schedule for breaks during your writing sessions. Even a 15 minute break can be really helpful.
4. Get sleep!
Whatever your daily schedule, make sure you make time for getting a solid amount of sleep. You may want to burn the midnight oil to get that last page in before bedtime, but if you have to get up for work at 9 AM the next day both your job AND your writing session after the job will suffer.
5. Work out a high level plan for your story ahead of the heavy writing!
Some writers are able to write on the fly quickly with no plan and have a product at the end of NaNoWriMo. Others struggle because they know they want to write something but they have no plan for where their story is going, increasing stress levels. Try doing the heavy conceptual lifting for your story before NaNoWriMo begins or at least early-on in the month. This difficult work up front will pay dividends when you do start writing pages with a plan for where your story is going, reducing physical stress.
With these tips you can maximize your NaNoWriMoexperience and have a better written product at the end of the month!