A hip person is cognitive of what styles are fashionable, and finds a style that suits his or her self, but doesn't necessarily have to be wearing exclusively non-mainstream vintage or designer articles. A hipster either copies a hip person, the other hipsters he knows, or whatever he sees in "Vice" magazine. A few fashion items are always acceptible regardless of how much of a poseur you are or aren't: Chuck Taylors, black hoodies, tight pants, etc.
A hip person might look hung over or like they just got out of bed, but if they do, it's because they really are hung over and just got out of bed. A "hipster" might spend considerable effort faking that look by messing up their hair and intentionally wearing wrinkled clothes. A telltale sign of a hipster douchebag is that he or she is clearly "trying" to be fashionable. They often overaccessorize with some sort of scarf, hat, or outlandish shoes, and put a great deal of effort into making sure everything matches.
A hip person most likely is an avid listener of music, but doesn't particularly care how others judge his or her taste. He or she might listen to anything, sometimes including things that were once, or even are currently, mainstream. A "hipster" contrives his or her music collection to be seen by others as cool and "indie". They love vinyl records. Crappy music seems cool to them as long as they listen to it on vinyl, and especially if it's some sort of rare recording that they can be sure no one else they know owns. If you asked a hipster whether he cared if people thought his music collection was cool, he would say "no", but he would be lying. They care.
In fact, the defining trait that seperates legitimate cool people from hipster douchebags is that truly hip people genuinely don't care what other people think of them, or maybe acknowledge it a little bit but don't base their whole persona around it. Hipsters are obsessed with this fact, and build their entire personalities in an effort to make it look like they also don't care. They want, just as much as normal people, to fit in. A really hip person just naturally fits in because he or she has a likable personality and is fun to be around. All hipsters hate other hipsters and consider them to be phonies, and no hipster will ever admit to being one even if they fit all of the stereotypes.
Claude: Omg let's go up to Williamsburg and go buy some ironic fashions at the flea market. Isn't it cool that we're 19-years-old and wear old people sweaters?
Felix: Yeah and then we can go back to my house and listen to Passion Pit!
Hipster: "I prefer to say I hipst. Excuse me, I'm late for a jam session at my parents house with my old high school buddies. We're gonna record our Indie rock covers on our old school tape machine. Oh yeah, and get this - after, we're gonna get high. It's awesome."