One key to writing a novel in a month is to silence your personal editor and just keep writing, even when you know the scene you just finished isn't quite right. Slowing down to edit what you have already written only slows down the whole process and keeps you from your word count goals. Save the editing for after the month is finished.
Set a specific time every day that you can dedicate exclusively to writing. Put a sign up and lock the door or retreat to a local coffee shop where you won't be disturbed. Plan to write 2,000 words every day during your dedicated writing time. This gives you a little bit extra to make up for days when the inevitable emergency drags you away from the keyboard or days when the words just won't flow.
If you find yourself going off on a tangent, explore that tangent instead of fighting it. Even switching genres midstream is perfectly fine. Your novel may veer off from a heartwarming tearjerker to an alien action thriller, but that's OK. You can decide later which threads you want to expand and which ones you want to cut. You also might find that the combined genres actually work well together and you've invented the next new trend.
If you've reached a point where you aren't sure what to write next, try adding some description. Spend a chapter waxing poetic about the scary castle your heroine just walked into or go into meticulous detail about the villian's tortured childhood. Describing every character, place and object is a good way to pad your word count and get your writing juices flowing again. You might even find some detail in your descriptions that can spur new plot twists.
Almost everyone who starts a novel writing month reaches a point where the story falls flat, the idea seems not as interesting as first imagined and the writing slogs in the mire of writers' block. Continue writing anyway. The point of a novel writing month isn't to come up with a brilliant masterpiece; it's to write a whole novel, start to finish.