Hi and welcome to Yorkie Talk. At the top of the "Health and Diet" section, there is a sticky titled, "VACCINES - An Overview". It gives general guidelines. I never give my yorkies the lepto vaccine, because it has been known to cause problems, and depending on where you live, your dog is at low risk. It is usually included in the Distemper vaccine, so I make sure my vet knows to give them "Distemper without Lepto". (He has to order it).
Also, check out some of the links at the bottom of that page. There are some expert opinions that are very interesting.