The best guide that I know of for training a young horse is Bertalan de Nemethy's book, "The de Nemethy Method." It will take you from the first time your horse crosses a pole to advanced gymnastic exercises; and it even shows entire gymnastic courses, with their proper dimensions. If you follow this plan, you can't go wrong.
Published by Doubleday, this book can be purchased on-line at:
http://equisearch.com/bookstore