While novels are (usually) made of chapters, stories are (usually) made of scenes. There are artsy exceptions, but for the most part your story is going to be told by scenes. Sometimes chapters have multiple scenes, and sometimes a single scene takes up multiple chapters. A good place to break a scene isn’t necessarily the best place to break a chapter.
Some writers recommend starting with scenes and then deciding where to break the chapters. If you prefer stories with multiple narrators, as I do, then it might be easier to write the outline as chapters first and then determine where the scenes fit in. Again, some chapters will have multiple scenes and some chapters will end before a scene is finished.
A scene is, essentially, a mini-story. It has a beginning, middle, and end. A scene has an objective and stakes. A scene asks and answers a question: yes; no; no, but; no, and further more. A scene often begins in a new location and ends when the characters move out of that location, but setting isn’t as good an indicator for the start and stop of a scene as the stakes involved.
So, to leap into the scene-by-scene development of your novel, ask yourself what problem your character is facing right now. Once you know the problem, find out how your character becomes aware of the problem. This is, usually, the start of your scene (from your character’s perspective). Then, ask yourself how your character chooses to address the problem. What does your character do? This is the middle of your scene. What is the result? This is the end of your scene.
Of course, storytelling isn’t nearly that linear. Sure, there’ll be scenes you need to start at the beginning and play all the way through to the end. But there will be scenes where you can start later and end sooner. You’ll want to use your best judgment in your outline, but you’ll also want to know as much as you can. When you write there will be some trial-and-error to figuring out the best places to begin and end each proposed scene.
You’ll want to know more than what happens, though. Where is your character? Who is with your character? What important details, emotions, and decisions will your characters face? Which character is narrating the scene? Who, among those also there, is the character feeling tense towards? Who, or what, else is the character tense towards? Who is tense towards your character?
You need to understand the points of tension and the sources of friction in order to know how to create satisfying suspense for your reader. You also need to know what’s at stake in each scene so you can help the reader feel the stakes.
Jot down an organized set of notes of what you know will help you realize the scene when you finally sit down to write it. You won’t know everything and that’s okay, but you’ll want to give yourself enough information to write the scene. You’ll also want to give yourself enough information to know what you’ll need in the previous scenes to set up this one, and what you’ll need in this one to set up subsequent scenes.