Having so recently emerged from the boiling kettle of devising an ending for this book, I thought it might be well to speak to some ending considerations.
I think of endings as a ziggurat - a stepped pyramid. Once the rising action of the climax begins, there is no going back down to the beginning level. Of course, there may be several parts to an ending, and you can have a short breathing space between them, but you don't want to let down and rest, as you might with story arcs earlier in the book. And the level step, or breathing space, should be short, compared to the elevation gain with each piece of the climax. Never let yourself lose the elevation gain.
Once you've reached the summit--the final battle, the climactic confrontation, the split, the bomb, the rescue, the cataclysm, the unveiling, the kiss, whatever it might be--it's time for a brief denouement. Contrary to popular misconception, the denouement is not the climax itself, but the winding up of threads, the actual resolution that follows upon the climactic events of the story. It is what you find on that summit, not the climbing action of getting there. And you notice that the actual area at the summit is much smaller than the base of the pyramid, and much smaller than the combined effort of getting to such a height. The harmonious shape of the ziggurat demands it.
So what are my rules of thumb wrt endings that my recent efforts (and six chapters in two weeks is definitely an effort for me!) recalled to me?
1. Don't introduce something new - a new power, an artifact we haven't seen, or a new character who is the exact locksmith needed to work things out. It's too convenient. It smacks of deus ex machina - and readers will throw the book across the room. You might get away with such a thing earlier in the story (though you shouldn't) but never, never at the end. Many people consider this a common flaw of fantastic literature - "oh, the author can make anything happen at the end, magic, reconfiguring the tachyon particles, or whatever. It's just too easy." I believe you have to make the rules of your magic or science or culture or alternate reality so clear that your climactic events can most definitely lead to failure. DOn't let it be easy.
2. Use people and events from earlier in the story to bind the whole thing together. If your story starts with a book (like Valen's book of maps in Flesh and Spirit) think carefully about what part the book plays in the climax. If you need an unlocking spell, make sure we know they exist in this magic system. If a dead body turns up, make sure your readers know the significance of that person (hmmm...oops...a matter for revision) and can feel the emotions you want to drive the conflict and climax.
If you are lacking the particular whizbo, person, or talent you need to feed the action, go back and put it (or him or her) in earlier - but seamlessly please. Don't hang a bright red arrow pointing to the golden ball that's just the right shape to plug the dike! The ball needs to serve a function in the earlier part of the story, too.
3. If you find yourself explaining too much, stop. Remember those short steps on the ziggurat? If you make one step horribly wider than the others, you've thrown off the balance. So look at what you're trying to explain and figure out how to salt in the explanations earlier, so that the reader will say, "Ah, yes. Wow! Of course!" as she is swept to the ending.
4. Be meticulous about your characters' decisions that lead them into and get them out of the climactic events. Explore all options. Why did he choose just the right path that would get him out of a jam? Let the climactic events flow naturally out of the building tension of the story, and your characters' dramatic reversals - maybe the thing they said they would never do - build upon the trail of evidence you've laid.
5. Did you tie off enough threads? Endings should not be a checkoff list, but don't leave the reader hanging with the big stuff. You want to leave readers with the feeling that life goes on, but you want to satisfy their most urgent questions. "Well did Gerick stay in Avonar or go back to where he had been living?" "Did Valen ever get a chance to have that great party he kept hankering after for a THOUSAND PAGES?" "Did Seyonne get it back?" (Well you have to leave some questions open...)
6. If there is to be a sequel, did you leave the right threads open? Is there a spooky undertone to the denouement? Check out the ending of The Soul Weaver (D'Arnath Book 3). At one time, it was the third of three books. When I discovered the "story arc" of Daughter of Ancients, I went back and modified the denouement. I'll bet you can pick out the pieces I slipped in.
Once you've completed those last chapters, reread your first chapter. Consider balance and symmetry. What were your hero's emotions, expectations, and opinions. How have they changed?
Consider the mood. Did you start off writing a farce and end up in a deadly, gripping battle for survival? Is your reader going to be confused that you started off a bedroom farce and ended up with a serial rapist threatening your heroine?
Or if your opening posed a mystery that turned out to be much wider and deeper than the original question, did you set the spooky music playing early on? Yeah. I think so. Cool!