Hopefully before attempting the NaNoWriMo you wrote an outline for your novel. If not, you will soon find yourself bogging down in the plot and not being able to carry on. Even if you did write an outline, sometimes that is not enough to steer around the muck and mire of the tar pits of dry, dull writing.
What follows are a few things that help me when I get stuck:
1. Sleep On It - One of the best things to do when you get stuck as a writer is to go to sleep. When you sleep, your brain mulls over all the things you were thinking about while awake. Often you will wake with new ideas and ways to solve the plot problems that plagued you the night before.
2. Take a Break - Go wash some clothes, do some dishes or some other menial task that requires little to no thought. While doing this, the active brain will think through those problems with your text. I have found that mental obstacles sometimes crumble when I do something else.
3. Have a Meeting - Call, visit, or I.M. a writer friend and pick their brain. Sometimes if you can have a meeting with someone who, like you, frets over every word, you can discover together the solution to your troublesome tar pit experience.
4. Read - If I get stuck, I usually pick up a book that I'm reading and dig in. After reading someone else's prose, I often find a method in their style that inspires me or a character quirk that resonates with my writer's soul.
5. Do Something Drastic - The most common cause of prose stagnation is our need to "tell" the story rather than "show" it. Michael Crichton once said that a good novel must have "conflict on every page". It is mostly true that the reason our prose flattens out is due to a lack of conflict, whether that be internal or external. Try infusing some drastic action into the prose that will put your characters in peril either internally or externally. In most cases it will floor the accelerator and drive your story right out of the tar pit.