Meet Koishi Minkus, Chibi's Furiend of the Week. Minkus was a random craigslist ad that claimed he was aggressive at 5 months old. His owners also said he jumped on their kids and scratched them. A 5 month old puppy that has had no training is expected to jump on people and be somewhat playful with other dogs because, get this: THEY'VE HAD NO TRAINING.
Please know what you are getting into when you adopt a puppy. It is a life time commitment. Not a ... until I have a baby commitment, or until I move, until I realize I have a 12 hour a day job, until I realize puppies have to be housebroken... IT'S A LIFE TIME COMMITMENT.
Check out Karen Pryor's Clicker Training for training resources. Also, check out local trainers that can help teach you how to train your pup to be the best it can be. Check out our RESOURCES PAGE for trainers that we recommend.