One of the major pieces of advice you'll likely get from anyone who's participated that I forgot to mention in the introduction. You do want to get ahead if you can. But here's the reason you want to get ahead - by the end of ONC, you need a story that is between 20-40k. In fact, you won't know how much over that word count you will get until you get to the end of the story.

Of course, one thing to keep in mind is one of the reasons the first round is shorter is because that round factors in preplanning for your novella, but even given that if you write every day, including the first day, it will take 250-500 words per day to write your novella. And if you write 500-1000 for half those days, you will make it to the finish line with your story. Pace yourself, and have a schedule if need be.

And don't wait until the very last moment to get it done!

Oh, and get the later word count done, you can work on polishing that while the judging goes on.