In my experience, people use the word "hipster" to refer to people who go to the same shows and listen to the same music and dress similarly to themselves, but are not as cool as themselves in some vague indeterminate way. Calling someone else a "hipster" basically implies that they are actively trying, but failing, to live up to one's own standards of cool. It's like a subculture-specific synonym for "poser."
Maybe this is just a regional thing, but around my way, the term "hipsters" represents the anonymous crowd of followers who are always present anywhere anything cool is happening but only because they are trying to use their presence there to make themselves look cool. Nobody tries to be one ... actually, people often live in apprehension that others will think of them that way.