Write every day
The key to “winning”, as in completing your 50,000 word first draft, National Novel Writing Month (NaNoWriMo for short), is to write every day. If you've ever tried to punch out 50,000 words in 30 days, you know that it's a lot of work. A lot more than some professional authors produce, so it's going to be a challenge for you too.
50,000 words in 30 days means that you need to write 1,667 words every day. But maybe you won't be able to do that, maybe you get sick, or maybe you just need a break from writing every now and then. Let's say that you decide to just write on the weekdays, taking weekends off. There are four weekends in November, which means that you're losing eight days there. That gives you 22 days to write 50,000 words, or 2,273 words per weekday.
In case you didn't notice, that's a lot of words. Again, even for a professional, so NaNoWriMo is actually a pretty demanding challenge.
Decide on a schedule and stick to it
The best thing you can do is decide on a schedule beforehand, and then do everything in your power to stick to it. Barring tragedy, you should follow your schedule, it's the law for November. If you intend to write every day, then make sure you write every day. If you're just going to do weekdays, then follow that. Just going to write weekends? That's going to be tough (6,250 words per day), but if that's what you're going for, then — you guessed it! — stick to that schedule.
The same goes if you know beforehand that some days won't have room for writing. Plan accordingly, and you won't be stressed out by them when they occur, in the middle of your writing.
50,000 words are a lot of words. Writing them is a lot of work. Your schedule is key.
Set a daily word count
When you're satisfied with your schedule, you can easily calculate your word count. Assuming your target length for the manuscript is 50,000 words (of NaNoWriMo fame — you could do more though, or less, but that will technically “fail” the challenge), you just divide that by the number of writing days in November. It's not exactly heavy math.
Your daily goal is the second law of November. Hit it, every day. Even if you think every one of those words sucked (bad days happen, you know), make sure you hit the goal, and do better the next day. The target here is to bang out a first draft during November, not to write a masterpiece in your first go. Remember this, because there will be days when the writing is hard, and everything reads wrong to you. Barrel through. Maybe you'll be surprised when you return to those awful words in the future, because sometimes they weren't so bad, they might even be good. It's hard to know when you're in the middle of writing.
Oh, and it's perfectly fine to write more words than your target word count. It's probably a good idea to not overdo it though, because this is a marathon, not a sprint. Something to consider when the words are flowing, perhaps.
Be prepared
Come November 1st, you shouldn't fiddle with outlines or do research anymore. You're now officially in the writing phase, so stick to writing. That means that you need to get all your preparations out of the way before then. This includes research and outlines, but also other things, like deciding on which writing tool you're going to use (BlankPage, hopefully), and informing your family and friends that you're going all-in writer fiend during November.
Have a writing space
Most of us don't have offices or cabins that we can use when we're writing, but that doesn't mean that we shouldn't have our writing space. You need a door of sorts to close when you sit down to write. It could be an actual physical door that signals to your family or co-workers that they need to leave you alone (you know, because it's closed), but there are other ways to distance yourself from the distractions of the outside world. Headphones, writing at a café, send your spouse and the kids to the movies, whatever works to give you your space so that you can focus on writing.
Having your own writing space is important. Nobody writes well if they get disturbed all the time. The people around you need to accept that, but the only way they can know is if you tell them. Or wear a big sign that tells them to go away, that might also work.
Don't stop, don't edit, don't worry so much Stick to your schedule, write your words, hit your word counts. Easy as pie, right? It is, until you start to wonder if you shouldn't change this, alter that, or maybe go back and tweak that shitty thing you wrote yesterday when everything was dark and sucked.
Don't do it. Don't edit your words, just keep writing. Don't worry about how the thing you want to be a book sometime in the future, but now more resembles an unpolished turd, are shaping up. Just write.
Seriously. Don't worry so much, just keep hitting those goals. It's a first draft, it'll be fine, if you give it a chance to be. If you deviate from the schedule, if you don't hit your word counts, it won't be anything at all.
Failure is always an option
In the immortal words of, err, some mortal fellow that I just can't remember the name of: “Life is hard, man.” These profound words of wisdom promises to mess with you all through NaNoWriMo. Things will happen, be it work or family or illness or something else, and you'll have to struggle to keep to your schedule, to hit those goals. That's life, and that's the big problem with a challenge like this. The universe don't care if you're doing NaNoWriMo, it's insensitive like that. You might fail. Try as you might, you might actually not make it through the month, following your schedule. If it's just a day here and there, you might be able to catch up, but you need to be prepared for failure.
And you know what, that's okay. Even if you don't write 50,000 words in a month, you still got some writing done, and luckily (hopefully?) there's another month coming after November. And one after that, until the universe can't be bothered to mess with us anymore and ends it all.
The point is this: Keep writing. NaNoWriMo is a fun challenge, but that's the only thing it is. Participate if you want to, beat it if you can, but remember that it's about writing foremost. That's the real win.