I am in the process of doing the same here is what I have found for starters...
www.akc.org is loaded with info and is very helpful! I have 3 books
Yorkshire Terriers by animal planet and The Yorkshire Terrier by Deborah Wood
I was given many tests to have done.
Bile Acid, complete blood panel, DNA, OFA certified, ears eyes and temperment tested, and have an experianced breeder and a person who shows dogs look at him to see if he is standard and does not deviate in a major way from standard. There are some breeders on here who have been VERY helpful to me and are helping me step by step. Remember DON'T BE AFRAID TO ASK QUESTIONS I have found out REAL FAST how rude some can be about breeding and their thoughts of "leaving it to the experts only" well you have to start somewhere (even the experts started somewhere) and asking questions and doing it right is a great start! I do encourage you fully to get educated about it and do it right if your going to do it...there is a lot more to it than, my baby is too cute not to breed. Health and standards play a huge role in this as we want to keep this breed as beautiful as it can be and as healthy as possible! I hope this helps and if you have any more question just ask maybe we can find out the answers together or a kind breeder in here will help us out!