I will second the Monks of Skee books. Best dog training books I have seen. They go into the research of puppy socialization and development. Very good.
Dogs are pack animals. Dogs have to have a place in the pack. Dogs settle their pecking order with a bit of fighting/playing. When we brought my wife's goldens together with my GSD we figured my very Alpha female and her very Alpha female would have a go at each other. We watched them very carefully.
Then the younger golden attacked the older golden!

Literally there was fur flying. We each grabbed a golden and put them on the ground by the scuff of the neck per the Monks. And then looked at each other with amazement. We did not see this happening. My dog was looking at the scene with this What The H... Was This All About?

The dynamics of the pack had changed and the younger golden was making a move for the Alpha position.
The old golden did not have a good leg to stand on. All four legs had problems. She got to a point where if the other dogs got to near her she would growl and nipp at them as a defense. The just left her alone and would look at her like she was nuts.

The young golden and my GSD settled who was boss in the backyard with some very physical play.
Putting the dog on the ground by the scuff of its neck is hardly violent and much less physical than what the two goldens were doing and going to do.
You do have to be physically able to put the dog on the ground and hold them there. But if you have them by the scuff of the neck they have a tough time getting up. My GSD only had to be corrected a few times. She learned real quick that if I grabed the scuff of her neck she just laid down.

Very smart dog she is.
We adobted a new golden who likes to counter surf. I fnally caught her doing it and put her on the ground. We then had a talk. She has not surfed since. She is however getting into the trash after we leave the house...
I found the Dog Whisperer to really know what he was talking about. If you see his show on TV its informative.
Later,
Dan