What you need is a strategy!
One of the things I’ve been using lately to hone my story for book 4 of this Portia Adams series is the concept of Chapter Synopses (in other words a synopsis for each chapter in the book).
This is not my idea of course, many people have talked about its usage including my agent and many others but I wanted to share it in case it could help you in your writing process.
Basically you write a short paragraph synopsis of each chapter in your book (proposed or completely written, I find this works at both stages). Try and focus on the action in the chapter (what actually happened) rather than details. Don’t worry so much about the length of each paragraph — some will be longer, some shorter. Also don’t worry about the number of chapters you have set out on the page.
Now if you step back and look at it as a whole you should see a few things:
1. Synopses that are really short and may indicate that this is not a new chapter at all and should just be absorbed into another chapter.
2. By the same logic, synopses that are too long may indicate you are trying to cram too much story into one chapter and it should be divided into two.
3. I don’t know if this is specific to detective fiction, but I also find this kind of layout shows me if I’m laying out the clues in the right order and if my climax and denouement sit in the right places.
4. You can do this for parallel story arcs, line up the chapter synopses next to each other to make sure they are progressing the way you want them to.
5. This is a trick I learned from doing this a few times, but what I find is that if there is no action in a chapter, it may be a chapter or a scene that can be dropped. If it’s just dialogue and the story doesn’t progress in the chapter, let it go, or at least put it aside and see if the story is stronger without it.
Chad R. Allen has a different goal in mind for his post on chapter synopsis but also has some good points about what works and what doesn’t.
Writer’s Digest also has some tips and tricks on synopses you can look at.