Even more, you need to not fear them and have the ability to command them that they accept you as leader of the pack. I was walking once and passed a yard and this dog came charging at me barking apparently going to attack. It tried to establish dominance.
My reaction? I attacked it instead, running at it waving my arms yelling and growling loudly.
That dog stopped dead in its tracks and looked at me as if I had three eyes and five arms and just stepped off a UFO. It was dumbfounded. It didn't know what to do. I glared at it and told it it better get back to its house if it knows what is good for it and it did, looking back at me once over its shoulder as it sheepishly walked away.
A buddy of mine adopted a dog that had been abused by a guy. When I came over, he kept it in a cage because my presence made the dog bark fiercely trying to tear at me through the cage like it wanted to rip my throat out. After a couple times there, the dog recognized my voice and saw that I was a friend of his owner. That dog and I became best pals.
When with dogs especially big ones, you have to establish that you are the leader of the pack and you better be prepared to back it up by controlling them because if they don't trust and respect you, you could end up being their lunch.