My flat-coat retriever was into heavy nipping when she was one month old. I tried the approach of screaming "OUCH" then saying "NO!!" really firm and putting her in the crate for 10 minutes. It took 2 days for her to get the message, which really amazed me that she figured out what I meant so fast. We're trying this approach with a new chihuahua puppy we have (Buffy) - so far it's been 3 days and she's nipping less, but we're still at it. Below is a link to pictures of my dogs. Hope you like them.
http://www.geocities.com/youngcasano...estFriend.html

Barbi