If you were ever wondering how to end the story you are writing, I may have some ways to help. I had a couple of tricks for figuring out the endgame of a couple of books. For Double Entry, at the penultimate scene, I literally had my protag voice out how I was feeling. I didn’t know what was going to happen next, so I had him literally tell that to his love interest, and wrote her reaction. It came together well, allowed me another moment to let them bond, and reinforced some of the themes I had been pushing in the book. Having them talk also clarified how the primary antagonist was going to behave during the final confrontation. So sometimes if you don’t really know where a story is going, it’s okay to let your characters articulate your uncertainty or frustration. It might lead to some new insights.
The other trick was to envision what a follow-up to the story would look like. If/when your book gets a sequel, what are some of the themes and ideas you’d explore? Where would you take your most important characters? If someone dies, how would they be remembered in your sequel? How would the sequel make things worse for your hero or heroine? Now, with those ideas germinating in your head, grandfather your climax and denoument to set up those threads in your potential sequel. Maybe you want your protag hellbent on revenge against his arch-nemesis in the sequel…so maybe the bad guy needs to do something deserving of revenge at the end of your current book (just an example. I’ve been talking with people in my James Bond fangroups on Facebook on why many of us have On Her Majesty’s Secret Service as our favorite bond movie, so that’s on the brain). And this would work even if you don’t intend for the book to get a sequel. I specifically let Calloway (my main antagonist in Double Entry) get away because I liked the idea of doing a hardboiled action-crime follow-up that was a complete shift in tone and theme from Double Entry, where Calloway goes on a mission to undo the mess he made in DE, with predictably disastrous, violent results. I never wrote the sequel because that would require more knowledge of the inner workings of drug gangs in Portland, OR than I have the stomach to learn, but leaving the door open for that sequel is what helped me decide Calloway’s fate in Double Entry.
I’m also a proponent of “just follow you character around and see what happens.” The only issue with that is knowing when to stop following. Where is the jump-off point where you know the main character arc of the journey has been completed, and a new one is about to start? For that answer, you have to look at where the journey started. When did the central problem present itself, and has the problem been resolved? The jump-off point, and therefore the ending of that arc, is when the prevalent problem comes to its resolution. And as a writer, you should be able to tell when that moment happens.
These are just a few of my go-to techniques for finishing stories. Please comment with any that you may have come up with. Here’s a book from Wizards of the Coast that handled its ending particularly well.