I seriously believe that Social Engineering in the real world and using it online are completely different ball games.
Like Monica said, Social Engineering is something that everyone does naturally. Whether they're good at it or not depends on natural talents and how much you've studied people and their reactions. In the end that's what it's all about. How people react towards you and what you say. But this is really more relevant to the real world than the internet.
On the internet, it is much harder to study people's reactions for obvious reasons. Someone can easily lie to you and you have no way of knowing whether or not they're telling the truth. There's no facial expressions, no tells, no emotions you can play off of. It's usually only text. Plain boring text that is hiding something much deeper.
But in a way this can also make it much easier to manipulate a person who isn't paying attention. It also requires no acting skills on your part. Just the ability to type bullshit at the right time. Say if you're using your talent to try and recover a guys email address so you can get into his AOL account and steal emails that he's been sending to some crazy corporate leader who wants to kill of all the whales in the world with a pickaxe. Something like that. Anyway, to do this all you really have to do is pretend to be his friend without ever having to actually see him or put on a front. And if he asks you a tough question you've got Google right there at your side. It just requires that you're smart enough to type out the right thing. No acting, no pretending, no sexual favors. It's much easier I think. Hell, if I wanted too I could go try and befriend some random person right now. I could change up my myspace profile totally editing who I am and what I do to suit there needs. Then just talk to him about his problems over AIM or whatever and in a few months I've got them eating out of my hand. I have done this before by the way.
In the end, Social Engineering is nothing more than observation and acting on what you've observed and a person's reactions. Sherlock Holmes would have been a brilliant Social Engineer despite his distaste for the mundane society he lived in. Actors make great Social Engineers. Good Poker players are brilliant at manipulating people. Lawyers, Detectives, and even salesman all make good Social Engineers. At least if they're good at their job they will. And girls tend to be better at it than guys I've seen.
Girls have more tact than many men do.
Really there is no way I can define exactly what you have to do in Social Engineering. But I can tell you that what I said above holds true. But it is unique to every situation.
I don't need my parents anymore. Google answers all my questions now.
"Whenever people agree with me I always feel I must be wrong."-Oscar Wilde