Books can be divided into two categories: An instructional, philosophical work OR a story pertaining to a personal life, whether that be fictional or non-fiction. A best-selling story pertaining to a personal life will not usually include instructional information as well but inspiration can still be found in the pages and the story itself.
In an instructional, philosophical, work, the purpose of the book should be clearly defined in the introduction. The book can then be divided into parts where each part addresses one aspect of the purpose of the book. Then, each chapter within a part should answer the questions promised to be answered by that part. You can draw a map to help you stay on track, to answer the part’s question and fulfil the overall purpose.
In a story, a chapter may be made up of one scene, or of a number of scenes. Every scene should be thought of as a small movie with a beginning, middle and end. There should always be a mission or goal associated with each scene.
Other ways you can ensure your chapter is purposeful is to build on your character’s profile, build the understanding that the character has of the problem and complication, move the plot forward towards the resolution, add humour or experiences your readers can relate to, or explore the subject matter in greater depth.
If one or more of these elements is not present at all and you cannot see a way to add it in, you might like to remove the scene altogether. You can always save the piece of writing for another story.