I recently ran a poll on Twitter (@JPRobinsonbooks) and found that my followers rate plot as being more important than any other aspect of a book. Other options were dialogue, moral point or research. When we're writing, I think we should really step back and look at the story as a whole. Where are we going with this? And at the end we should ask ourselves if all loose ends have been tied up.
I make a list of "loose-ends" as I'm writing and at the end of the book, I check off everything that I've noticed. This prevents things from "slipping through the cracks."
What about you? What are your strategies?