Depending on how well you've digested your sources and research materials will likely determine how organized your chapter outline will be. That being said, get to know your sources intimately. If you do, then you will be much better off. The word will come easier, flow better.
Writing a chapter of a non-fiction book is a lot like writing a large explanatory essay. The thesis is what the chapter is about, so as long as you write a chapter focusing on bear dietary habits, in a book about bears, you will be fine. There will be subdivisions within your chapter. See below.
Topic AAs you write the formula of the entire chapter will change as your ideas consolidate, so be flexible.
The big thing that I encountered when writing my last chapter of my Sandman book was the progression of ideas. What is the best way to tackle a topic? I asked myself that many times. The best answer I can give you is feel out your subject. I was writing about Christianity and the impressions it makes on Sandman over the course of the entire 75 issue run. So at first I was writing things down, thought by thought, then I tried to do it by issue of appearance. Eventually I settled into archetypes, and worked my way through the biggest topics I could write about under Christianity. I wasn't afraid to elaborate on the small stuff either, simply because I must assume that the reader knows nothing about the source material. It also ensures that I explain my thoughts simply and concisely.
Take these things into consideration and your ideas will congeal faster.