Whatever is hidden behind the curtain must be revealed at last, and it must be at one and the same time completely unexpected and inevitable.
By the end of the story, all primary and secondary plotlines have to be addressed, all character questions have to be answered, all conflicts have to be resolved, and you have to do it without relying on coincidence or contrivance. In order to accomplish this, you need to track plot and character details, which can be an organizational challenge. My Triple X Strategy will help you manage the process.
Step One: Anytime that your book mentions an issue that you know you need to resolve at some point in the future, or ...