My yorkie used to bite me too when she was around 3 months. It started off with soft bites, but I never let her know it was bad so soon, it turned into hard bites. That's when I was like oh no, I should've taught her that it's not right. So I read somewhere that if they do something they shouldn't do, you tell them no and show them and then leave them alone. Soon they get the idea that when they do that you're going to ignore them. So that's pretty much what I did, if she'd bite me I would say "OW! No biting." And then I would put her down and walk away. She doesn't bite me anymore.
Some books I've seen at the library are very informational, for example this is the latest one I read and it was very good.
http://www.amazon.com/gp/product/cus...283155&s=books