In a class I taught, I drew a diagram of a river on the board to illustrate this. "This makes it very easy. I just put heightened moments of tension at each bend in the river," one student noted. "Maybe a big decision, a change of heart, a new understanding. Or an external shift, like a move or a marriage or a big loss." It made a big difference in her book structure to finally understand these "emotional peaks:" to view her scenes, chapters, and manuscript like a flowing river.
A reader from Cincinnati attended one of my classes and sent a followup question about these emotional peaks. "You mentioned the emotional shift that happens in our writing, and why it's important," she wrote. "Could you help remind me with what needs to go along with emotional shift in terms of dialogue and setting, or strategic placement in story arc?"
Start with the Larger Story
First, learn to view your book from its larger story. In my book structuring classes, we use a storyboard to analyze the structure and the "peak" moments. You can also draw a winding river on a large sheet of paper and ask yourself about the main turning points. Place them in the bends of the river. On the storyboard (see my video here), we use a W diagram, which makes it easy not only to see the turning points, but also the tone of what comes before or after each turning point.
Once you have in mind the emotional shifts in your larger story, begin to look at each chapter. Chapters require some shift in the external story or the internal story. In other words, something needs to happen to make a chapter a chapter. When I work privately with writers at my annual writing retreats or through my retainer program, I set them up with a chart to easily tell which chapters have enough of a shift, and which are just taking up space. Once you see the duds, you can add an event, a realization, a moment of emotional shift.
Working from larger story to small units of chapters is a sound plan--it keeps the book cohesive. If you change chapters around but don't keep the whole book in mind, the book can begin to fall apart structurally. It's happened to many writers. Sometimes, it's not easy to recover the book.
Once your chapters feel like they have an emotional peak, or a shift, you can begin to work on the placement of elements to precede and follow the shift.
What Comes Before, What Comes After
There are three types of scenes: setup, action, and reflection. Most emotional peaks happen either in the action or reflection parts of scenes. I think successful scenes nowadays (in any genre--even nonfiction) usually have a smaller amount of setup and more action. This wasn't always the case--we've changed as a reading culture and want a faster pace in our literature now.
My students learn to analyze how much setup, action, and reflection they have in each chapter. Most have too much of one, usually setup or reflection. These don't deliver the emotional peak without action. We readers need to see something onstage in front of us (an example, an illustration). Readers don't believe a change that's just talked about or thought over. They need to actually see it. Makes sense, right? Same with you, in your life, most likely. Deeds speak louder than words.
So your first task is to make sure you are showing the change (show, don't tell comes in very handy here!). You can have setup, and you can have reflection, but if you don't have action, it's not going to be believable.
To answer the reader from Cincinnati, step back and look at these three elements in every scene you're questioning. Make sure you have action. That will make a huge difference in how much readers follow the bends in the river of your scenes, chapters, and whole book.