Bonafide Business Plan?

I am sure many on here have actually done a bonafide and exhaustive business plan. I am just now doing a little research on how to do one. It seems daunting at best and down right impossible for some things. But since I have been looking at how to do it correctly and I thought I would share something in an article I just read so others might take this step to help grow their company.
"If you don't know exactly where to start, or get confused about what is really supposed to be in it, pick something in an outline that you do have knowledge about. Start there. Build up your confidence and keep moving through it."
I bring this point up in particular because it really took a load off of my shoulders. I had (have) no real idea of how to get ALL of the important info (or exactly what that is) and put it together. It is going to take me a long time to get through but I want to have a good living document to work with so I'm putting in the time.

Maybe some can chime in with their advice or anecdotes?