I attempted NaNoWriMo before. Never managed to succeed at getting down 50,000 words, though, so take it with a grain of salt.

The best way to get through NaNoWriMo is to see if you can find at least one person who's willing to do it with you. Having people to nerd out about your novel with, to talk to you about what they're writing, setting up times when you write together - that is very inspiring and motivating! And you can keep each other focused. In person, there's just something about hearing another person type and knowing they're writing their novel, too, that makes it so much easier to focus! At least, for me. ^_^

Another thing you can do is if you're in the middle of novel writing but then get a totally different idea for a novel, or want to write something else, jot down that idea somewhere! Maybe do a short summary of your thoughts. If you don't feed that inspiration a little bit, then you're gonna be progressively more dissatisfied with what you are writing for your novel. But then try to get back to your novel . . . maybe incorporating the other idea you have that's inspiring you into it! Who says you can't write about a vampire romance in a sci-fi adventure that takes place on many planets and includes time travel? It's your novel! Maybe you like the characters in your other idea more. Okay, bring those characters into your novel somewhere!

If you just, have no inspiration one day for your novel, a trick is to go onto another document and just write about how you have no inspiration today and whatever life stuff is going on. Writing it out can help you articulate your thoughts on it, free up some clutter in your mind, and hey, now you've written something. Perhaps you can even use what you wrote there in your novel somehow!

At the end of the day, you have to do what makes your novel writing fun for you. And if it turns into a mishmash of a whole bunch of disjointed ideas, who cares?