As I'm tentatively poking at a couple of my novels that have languished for a while, I thought this recent checklist she posted would be useful to me and hence I'm passing it on.
Seventeen questions to ask your novel
As Emma says in the comments, you don't need to know all the answers upfront, but even if you're a Discover-The-Story-As-You-Write sort of writer, you ought to know the answers when the novel is finished. If not, it probably needs a little more work. :)