agressive puppy?

Question
I have a 3 month old female rott/chow. I don't know if it's just because she's a puppy but out of nowhere when I'm out walking her or just walking by her in the house she attacks my leg's and bites me. When I say no in a firm voice it only makes her growl more and bite harder. I pull her off make eye contact and say no again. She just keeps attacking my leg's. I try not to yell, I've never hit her, I just don't know what to do. I saw a product online for agressive behavior, like a medicine. Should I try it? I know you'll most likely say obedience training but I've heard nothing but bad thing's about it. Please help. Thank you.

Answer
You're right, I am going to say obedience training.  However, I will agree that unfortunately in far too many cases, it is a useless waste of time.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  For more on being top dog, see http://www.dogbreedinfo.com./topdogrules.htm

Yelling ''Ouch!'' and walking away can be a very effective technique for the biting.