Go with Mrs Toast, AA etc, disregard dominance "theory" and avoid trainers who advocate dominance based methods. Here's why:
Back in the 1940's, Schenkel studied wolves and published his findings. He observed that wolves live in a hierarchical society with the Alpha being the dominant wolf. David Mech later popularised this idea in one of his early books.
And so the idea spread... dogs are descended from wolves. Wolves live in a hierarchical society, and so "we" must dominate our dogs to let them know who's boss.
It wasn't Schenkel or Mech who put forward the idea of dominance "theory" with regard to dogs, it somehow became "common knowledge".
A few points:
The wolves that Schenkel studied were not a wild wolf pack living in their natural environment, but captive, made up of individuals captured from different locations. Modern studies have shown that wolves live in family groups with the parents being at the head of the family.
Schenkel misinterpreted the behaviour of the wolves he studied with regards to pinning others to the ground.
David Mech later withdrew his support of the dominance idea.
Also, dogs are not wolves. They are by now a separate species. To try and put a wolf's behaviour on dogs is as ridiculous as putting dog's behaviour on wolves. We wouldn't bring a wolf into our homes and expect to be able to control it. Why? because a wolf is a wolf, not a dog.
Years back (before I knew better), I pinned a young dog to the ground to show her who was boss. Quite frankly, I felt like crap afterwards. Don't do it - it does nothing for your relationship with your dog.