For normal people, NaNoWriMo is a hectic time. In addition to a full time day gig, people have family and personal obligations, which makes NaNoWriMo one of those things that's crammed into the spaces between life and work and sleep (well, sometimes sleep is skipped). So for normal people, a writing schedule is key to reaching that magical 50,000-word finish line.
[Please note: I'm emphasizing "normal" because some of us are fortunate enough to work from home, so scheduling is less of an ordeal. This post is directed to those who work a traditional full time job (we'll say 9 a.m. until 5 p.m. for the purposes of this discussion).]
When you create a writing schedule for NaNoWriMo, try to keep it as routine as possible. If you switch around your timing too much, you may forget when you're supposed to be writing, and before you know it you'll be 30,000 words behind where you should be.
So if you get home from work at 6:00 p.m. Monday through Friday, schedule your writing time for, say, 8:00-10:00 p.m. Monday through Friday. This regularity ensures that you know that between 8 and 10 every evening, you're writing. That's not to say you would only write between 8 and 10 at night, but as long as your time is regular, you'll be much more likely to stick to the schedule.
Something else you should keep in mind as you create a writing schedule is the minimum daily word count for the event. If you write 1,700 words every day (including Saturday and Sunday) during November, you'll reach 51,000 words by November 30th. Allow enough time each day to reach your minimum word count for that day. If you go over, wonderful, but if you go under, you'll need to make the word count up on another day. If you have a tight schedule in November this may not always be possible. So plan to write around 2,000 words each day, just to be safe. That includes weekends, by the way.
As you create your schedule, try to do what works for you. If you can't write in long stretches on the weekends, try scheduling short spurts throughout the day, taking frequent breaks. Don't force yourself into a schedule you know will burn you out before the end of the month. That's a very counter-productive way to work.
Once you work out your writing schedule, commit it to paper. Post it in your writing space, as well as a common area that will allow family members, friends, and roommates to see it. It's important for those around you to know when you're writing so they can give you the time and space to get your work done. Having the schedule on paper may also help make it more concrete for you. That works for me; if I see something on paper, it carries more weight than if it's just on my computer or in my head.
Finally, remember to be flexible. Life happens, even during NaNoWriMo. So you may not be able to stick to your exact writing schedule every day. And that's okay. Steal an extra half hour of writing over breakfast before work, or on your lunch break.
Remember that NaNoWriMo is not life-or-death writing. It's meant to be fun. So don't take yourself or your schedule too, too seriously. Just write. And enjoy it.