A semi-agressive puppy

Question
Dear Labman,

A little over a month ago I adopted a St. Bernard mix puppy (approximately 6 weeks according to the shelter though I think he was younger) as a companion for my Golden Retriever because we are expecting a baby and I was worried that the Golden would be very lonely.  He is very smart and was quickly housetrained (within a week) but I am having a problem with him showing agression towards me.  On 2 occassions I have caught him trying to get into the trash.  I lightly popped him and he was very quick to turn around and very viciously attack my hand.  Both times he drew blood and he is now only about 10 lbs! Although he is very sweet and loving at all other times, I am worried that when he is 60+ lbs that he will attack our new baby and that would be devastating.  Do you have suggestions on how I can show him that I am boss and that he cannot attack me or anyone else?

Answer
Having a good pack structure reduces such problems.  The 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/

Likely you will need stronger corrections.  Give a warning stern "Bad Dog!".
In stubborn cases, I repeat the "Bad dog!" right in its face with the dog on its back. Hold it down until it lifts one back leg to show submission.  Use one
forearm under his jaw to keep his teeth away from your face.  Another very
effective technique if the dog is small enough, is to pick it up with your
hands behind its front shoulders and hold it out with its back to you.   Make
sure it is far enough out it can't fling its head into your face.   Hold it
until it quits struggling and relaxes.  If you can't do either of those, try
the squirt bottle.  Fill it with water and a little vinegar or lemon juice.
Give it a squirt in the face as soon as it misbehaves.  Dogs hate that.  I do
too and only use it in desperation.  Denying it your attention works great
too.  Turn your back, walk off, whatever.   Dogs are very social, and losing
your company is the worst thing that can happen.  The solution to a stubborn
dog is an owner that is even more stubborn.  Don't forget the praise and
petting when he finally yields.

You really must take control of him.  Many people say never leave a dog alone with a child.  With what will be such a large dog, and one that has shown maybe more dominance than aggression, you will need to be even more careful.  Remember, a dog's personality isn't mature until 3 years old, and before than, it can take an unexpected turn for the worse.