1. Commit to your project. Know how many words/pages/chapters you want to have finished each day/week/month and stick to that. Even if your first draft is terrible, at least make sure that you actually have a finished first draft by sticking to your commitment.

An easy way to do this is by rewarding yourself for reaching your goals. (When I finished NaNoWriMo I bought myself Ben & Jerry's ice cream to celebrate.) Another way is to promise your readers that you'll upload what you've written every day/week/month etc. For most people it is (for some reason I'm not aware of) easier to keep promises to someone else than to themselves.

2. Force yourself to get into the story. Draw maps, print out pictures, make family trees and so on. And you don't have to store them away in a drawer or a binder. It might help you to cover your walls with them.

2. Stop writing when you still have inspiration left. It may sound a bit weird at first, but think of this: if you stop writing because you don't know what to write, you're less likely to continue it the next time because of a writer's block. Puting away your work when you still have inspiration left, is like stopping at the hight of your career: you prevent a downfall.

3. You don't have to write the project chronologically. If you come up with a brilliant chapter/scene, just write it down so that you can use it later. It would be a shame if you would have forgotten about your idea by the time you could use it in your story because you're writing it chronologically. If you do want to write chronologically, just add the scene to your story overview. Even though the vibe will be different when you finally get to it, you will be able to write it.

4. Make sure you know were the story is going. This way you won't get your characters into situations that you can't get them out off because you haven't thought that far ahead.