The universal custom before reciting “oseh shalom” at the end of the amidah is to go back 3 steps – left, right, left. However there are poskim who write there should be 6 steps backwards,  namely three steps with each foot, and this is done as follows:  left, then right to make it level with the left, and the same thing is then repeated twice more, thus making a total of 6 steps backwards. (see: Divrei Chamudos on Rosh, Berachos, perek “ain omdim” paragraphs 67 and 68; Machatzis Hashekel Orach Chaim 123:10)