I would strongly recommend the following 3 things:
1) Get a "Mini-Mentor." Someone who has bred minis in the past/presently breeds them, shows, etc. You can find some experienced mini-folk at your local Miniature Horse Club.
2) Go to LilBeginnings.com and read up. Make an account so you can take part in their WONDERFUL forum, miniaturehorsetalk.com that is full of many experienced breeders, showers, drivers--anything mini-related!
3) Buy the book, "Miniature Horses: The Veterinary Guide for Owners and Breeders." (Click http://www.amazon.com/Miniature-Horses-Veterinary-Owners-Breeders/dp/1570763984/ref=sr_1_1?ie=UTF8&s=books&qid=1263173868&sr=8-1 for amazon page where you can "look inside" the book/order it.)
Hope that helps! Keep us updated.