http://online.wsj.com/article/SB10001424127887324637504578567414083664112.html
From my limited experience, what really helps is to have this feeling of unconditional kindness (which has to be cultivated through practice). This will alleviate any fear that we may have. Dogs (or any animal for that matter) sense and perceive fear as negativity and might attack simply because of that perception that they get from us.
They will also sense kindness and goodwill; and they may reciprocate in a non-aggressive way.
I remember in 2006 when I joined a group of ladies to do the Puchong Dog Pound rescue, we managed to carry all the dogs out though they were earlier frothing at the mouth and snarling viciously at the dog pound workers. The workers thought we could talk to dogs, simply because we knelt down and told the dogs we were going to save them. It wasn’t that at all. We were driven by an urgency to save them and the only way to do it was to carry them out onto the lorry as we had a deadline to meet (or rather, to avoid the vet who was coming to euthanise them). That sense of urgency shelved all our fear and this was despite the fact that personally, I had never handled pound dogs before, or large dogs for that matter.
All I remember in those moments was a compelling urgency to save them, an urgency driven by compassion.
For the full story, Chapter 3: http://animalcare.my/wp-content/uploads/2011/04/Pawprints-on-My-Heart-e-book.pdf