I found this article on novel endings and it was incredible helpful.
I decided to extrapolate the key facts and place them here as a lovely reminder. Because I really need to start thinking about my ending before I start editing.
The commandments of great endings:
1. Tie up all lose ends
At the end of the book, make sure to tie up all the loose ends except for one so that you leave the readers wanting more (particularly if you're writing a sequel).
2. Make the ending inevitable
Readers should feel like there is no other possible ending based on the character's choices and scenes leading up to it.
3. Characters choices lead to the ending
The ending should come as the result of choices made by the characters. It should be foreshadowed in the scenes that come before it.
4. Something must end
Even if you are working on a series, something must be resolved by the end of the book. Whether subplot or a plot thread. The circumstances must also end, so if there is a sequel, those circumstances will be different.
5. Something must change
Avoid endings where nothing changes. Whether it is character personalities, emotions, viewpoints or political systems--change something. Otherwise, your reader just wasted a lot of time.
6. The main character must change
Which means the character guiding the story (narrator or focal character) must change in one way or another.
7. Avoid Deux ex Machina
Do not let a natural phenomenon or coincidence solve the dilemmas of your story. The Greeks may have gotten away with it, but you cannot.
As my current ending is pretty darn awful, these rules will be very helpful. In fact, I plan to focus on how my story will end first and then work backwards.
We'll see how that goes.