Once upon a time I wrote a business plan for a restaurant. I had no idea how to start, so I went to the book store and picked up a couple books on "Writing a Business Plan" and read them. Because I learn best through doing, I started to put my plan together as thoroughly as I could. Next I asked to see other people's plans, I found some online to use as examples and lastly - I took my plan to the local Small Business Development Center (a non-profit that consults on growing small biz) and met with a counselor there for free. He read my plan and critiqued it so that I was able to improve it. 

I second what @EmilyCowan said about reaching our to your peers or to others who hold the knowledge you want to gain. Networking is always a great way to educate yourself.