Lacking an education or background in writing, I relied heavily on my local library to assist in my efforts. I found many books on how to write non-fiction - some good, some not so useful. I discovered there is no silver bullet - no single book that says it all. Search for a "how-to" book that strikes a chord with you -one that is relevant to your work.
I also found it extremely helpful to go back and read a second round of "how-to-write-non-fiction" books once I was well into my project. The information sunk in much more easily and made more sense. I was able to edit my work with a whole new set of professional tools.