Give every chapter a purpose
Before writing, summarise in one line what the chapter must accomplish. If two chapters have exactly the same function, they may sometimes be merged or made more distinct.
Use subchapters sparingly
Subchapters are useful for separating scenes or viewpoints without creating too strong a break. They should improve reading, not merely act as filing labels.
Track progression on a timeline
Linking events to chapters helps check chronological order, the duration between scenes and character movements. It is particularly useful for stories with several plot lines.
Reorganise without breaking the manuscript
A tree structure lets you move parts without copying and pasting large blocks of text. After a move, check transitions, time references and what each character knows.
Put these ideas into practice in one workspace
The callen-jf.com Writing Studio lets you move directly from advice to practice: write, structure the manuscript, prepare characters and chronology, then export and format the book. The account is free and the tool remains separate from the public pages of the site.