So new to the industry, I only recently read (and realized, duh!) that YA and adult books do not have chapter titles. But what's the fun of that? It certainly didn't stop me from putting them in my YA cross-over "Pardy Boys" draft. And though I know I'll have to take them out (wah!) for a more market-aware professional look, they have really helped me define sections of the book. It's one of the tricks I learned in screenwriting. Yes, my tawdry Hollywood past has come to haunt me (I feel like the poor girl in 1984's "Angel", tagline: Honor Student by Day...Hollywood Hooker by Night.)
In screenwriting, the script is broken down into "beats", much like paragraph breaks might represent the scenes of a novel in an extensive book outline. But an extra recommendation to really fully illuminate your intentions with each beat is to give each movement of the script (or book) a chapter title. And though you can't keep them for your book, chapter titles are not only kinda fun to write, but give an instant road map to where your novel goes. And if you insert a Table of Contents (using Word's "insert: reference: tables: toc") you will literally have a one page listing of your chapters. Think of it as an at-a-glance reference tool.
I found this really useful when dividing the book into its chapters without being limited to just the stale breaks of "chapter 1...chapter 2...", etc. Dividing chapters into fairly even breaks of 5 to 10 pages is a great start, but chapters don't always break evenly when a chapter is often unified by a theme, goal, or pursuit for the characters involved. Chapter titles make it much easier to see where the story breaks organically. After you find those natural breaks, you just take the descriptive titles out, leaving the professional chapter listings behind. Your reader/agent/editor will never know you dipped into the customs of a chapter-book, but they'll definitely be caught up in the powerful rhythms of a book that has its own ebb and flow.
Now get back to work!