The difficulty of structuring a book into Chapters

I never knew how difficult it woould prove to be to find some kind of relevant and logical sequence in which to place chapters of the book i am now just finishing and about to publish on the 15th of July (2010). Many factors make it difficult to keep each section to its own subject and not cross over into something that has already been mentioned in earliuer chapters. This is because some topics are connected.For example, Por Gae Masks and Wai Kroo - who is Por Gae??
It has to be wondered whether one should explain about Por Gae first, or Wai Kroo??

Publish Your Nonfiction Book: Strategies for Learning the Industry, Selling Your Book, and Building a Successful Career

In the end, i just write what i feel is important, and think that if there is the odd repetition of info about a certain matter, it will in fact also help for the reader to feel more familiar with the things he or she reads about in the book, and help to remember the info to.
Above Pic; Por Gae Ruesi Dta Fai mask.