All of the above. And none, really. Social interaction isn't a spectator sport, but those of us born with less aptitude can sometimes benefit from guidance. You don't get these skills by observing them, or reading about them, you get them by GETTING them. God, now I sound like I'm quoting David DeAngelo. He wrote a pretty good article about why it is that very intelligent men often fail with women. Very informative stuff, really. Social skills come when you are habitually doing those behaviors that will allow you to negotiate successfully with other people. And it comes from mostly from attitude.
But don't ask me much more. It'd be like asking a dude in a wheelchair for some advice on winning the marathon.
My social skills didn't kick in until a year or two ago, but before then the process was very painful and very gradual. I'm usually a quiet guy and I hate crowds, which I'm sure isn't uncommon here. The most common adjective that people predicated to describe me was "creepy", when I wasn't even trying to creep anyone out! But then I learned to be interested in people, make them feel comfortable, enjoy the moment, and that most people STILL don't matter in the end. Only a select few individuals, like those that can help me attain my aspirations.
Another important lesson I learned, through painful years of useless failed connections, is that most women suck and aren't worth my time. The old adage that "Opposites Attract" is, in my opinion, correct in theory but B.S. in practice. My girl is an Aspie, and I wouldn't want her any other way. 
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"And lo, the beast looked upon the face of beauty. And beauty stayed his hand. And from that day on, he was as one dead."