Goodness there are so many people who do this and it bothers me so much!!! I am guilty of it to and it bothers me even when I do it and I am in recovery from the "really" disease.
You start saying a story to your friend about something out of the ordinary that happened to you, "When I was on my way here I almost hit the emo kid that had his hood up and was obviously listening to music, i came within inches of hitting him and he didn't even know it ever happened,"
The reply, "Really?" NO NOT REALLY I JUST TOLD YOU FOR NO REASON! who started this? who was the person who started spreading the "really" disease? It is really annoying!