I'm trying to understand the concept of flirting but I just can't figure out how to flirt. I've been lurking for awhile here, checked out the sidebars, checked out askseddit but I still can't understand it. What is flirting and how do you do it?

EDIT: Another important question that came to mind is how do you transition from a casual conversation to a flirtatious one? Or do you flirt during the casual conversation?