As someone who attended an "elite" college, I can assure you that you only need 3 things to get into them:
1. A plan to follow (you can easily find great ones online these days) telling you what to do in high school (with respect to classes, extracurricular activities, volunteering, leadership, standardized tests, recommendation letters, etc.)
2. Money (i.e., live in an relatively affluent area with a good public school or attend a good private school)
3. Determination (lots of it)
Your personality doesn't matter at all for anything other than the interview, which you can also pass with flying colors as long as you have basic acting skills (which can be easily learned as well). Basically just smile a lot and don't act like a psychopath at the interview, and you're good to go.
As for getting into a specific college, that's a crapshoot. The admissions process is a black box, and there's no way to guarantee admission to a certain university unless your parents are big donors. But if you apply to, say, all the Ivies + Stanford + MIT, you're guaranteed to get into at least 2 or 3 if you have the 3 things I described above.
In that system there's a series of successively narrower hoops you have to jump through - if there's only one junior high that teaches math beyond a certain point and not everyone can go there, those kids are going to be better prepared for the high school that teaches more advanced things, so they'll make up a disproportionate amount. Since it's really hard to on the track once you're not on it, at every level of evaluation and selection you keep selecting out of smaller and smaller sections of the initial pool.
The people who come out of that system tend to be supremely competent, but in a limited way. If you take a stand in high school approaching a topic from a different angle and a teacher doesn't like it and gives you a C (the horror), when it comes time to apply for Harvard there are an essentially limitless number of competitors who didn't and who got the A. So people who naturally play it safe and cynical tend to move on, and people who don't tend to adapt or get cut.
Fair disclaimer, the article is over a decade old.
http://www.quora.com/College-and-University-Admissions/What-...
Most of schooling is complete crap that you'll never use, or in the case of computer sciences especially it is outdated and/or barely practical by the time you graduate and get a job.
What schooling is important for is teaching how to collaborate and how to learn. Most of the learning you'll actually use on the job is stuff you'll learn on your own or after you are hired by working with other people.
In my opinion from what I read in this article these students working together to figure out a tough test and collaborating are using their brains and learning how to accomplish things. That is vastly more important than an arbitrary, contrived, academia model of learning.