I'll be upfront. I've never participated in NaNoWriMo (and have no desire to), but I've observed many writers go through the process.
I know it can help writers put aside perfectionism, procrastination, and inhibitions about writing.
That is: It motivates a lot of people to SIT and WRITE.
One might tend to think: Well, this is a good thing.
Sometimes, I'm not so sure.
When unskilled or unpracticed writers attempt NaNoWriMo, they inevitably end up with a lot of material they can't use.
Sometimes they don't realize they can't (or shouldn't) use it. Sometimes they even think they ought to submit it. (That's actually the least of MY concerns, though it does concern some agents on the receiving end.)
My concern is that NaNoWriMo could be immensely productive, for any level of writer, if approached with a bit of preparation.
Technically, such a thing might be called an outline.
But I call it laying the foundations for success.
What's going to happen in the story?
What does the character want?
What will the turning points be?
Right now, I'm working on a project for Writer's Digest, a 128-page bookazine (a special newsstand-only "book") that focuses on how to produce a novel draft in 30 days.
It is possible, but I'd argue you won't get anything meaningful out of it unless you have an idea of what you want to accomplish.
Otherwise, you're just writing to write. Maybe that's OK.
But I'd like you to have something at the end of November you can build on.
Here are a few excellent posts that will help you prepare for the NaNoWriMo challenge in a meaningful way.