How do you become invisible?

Just looking at the work of wedding photographer Jeff Ascough. I want to know how he manages to be invisible in a room full of people. The subjects in his images seem like they are unaware of his presence. Does he just kind of stand in the corner of the room and take pictures or are people so comfortable with him that they don't even pay him any attention? Any insight on how he works? Techniques? Because the way I currently shoot, you know that I'm taking your picture. Kind of loses the spontaneity.