When I first started teaching, I found it really helpful to buy a few books on learning the guitar. The authors have usually figured out some pretty good methods of going from one step to the next and you actually find some additional lessons to teach that you wouldn't normally think of on your own.
Don't plageurize or anything, ...just use the books as a guide to come up with your own curriculum. After awhile, you end up coming up with your own 'book' as you type out lessons and photocopy them for your students.