Organizing a rule book
One issue is staring at this blank canvas of a rule book and not knowing where to start.

To find out where to start, first realize exactly what you're trying to accomplish:

Tell someone how to play.

I might suggest you show the game to a few friends, preferably the most interactive ones. If they ask questions, then when you explain it to another friend, you have the insight of what they may be thinking and the ability to answer just what's on their mind.

You will learn exactly what to write by sheer redundancy of explaining the rules over and over, and subconsciously you'll build a structure of your explanation that you could use while writing your rule book.

Hope this helps you getting started.