So, if you were fortunate enough to be among the few who "won" NaNoWriMo (41,940 of 300,000 participants), congratulations! Give yourself three big cheers.
But, if you're like me, you're wondering now what? This year's NaNoWriMo writing project was part of a 90,000 word novel I'm writing, so it might be a little different than you if you've actually written a novel from end-to-end over those 50,000 words.
The next larger step is to create our second draft and there are an infinite number of ways you can go about that. One suggestion is to let some time pass and allow yourself to put some perspective on your work. I tried to do that one year and I found that I had lost a lot of momentum and it took almost half a year for me to really get back into the project.
So, I'd recommend you continue working at it, building off the momentum and euphoria that you currently have. The approach I'm trying is to write a treatment of my story, a synposis, maybe 5-10 pages of everything that has happened in my story. In that compact form, I think I can work with the story structure and identify its weaknesses before jumping into any kind of editing or re-write.
Take time to make sure you have all the pieces in your story in the right place and that every chapter and scene builds towards the climax and drive the plot forward. It can be terribly difficult at times, especially if you're struggling with a scene or chapter that you like, but you also know just doesn't fit. Yank it and come up with a new scene or chapter. You'll be surprised that it'll probably be better than the one you first wrote and will also be a better chain link in the overall story.
Best of luck!