Let me start with a disclaimer. I tried NaNoWri National Novel Writing Month once about six years ago. I wound up stopping about halfway through with a tangled mess. It taught me that I really have to have one scene written up to the level of a semi-polished draft before moving on. But it was the eighth novel that I both started and finished. So it’s not entirely surprising that I have some writing habits that I couldn’t overcome.
But the goal for all writers once they finish a manuscript is to sell it. My essay called Prospecting for Gold Nuggets gives some reasons why it’s important to think about a book’s premise early.