You ought to tell us how old you are (assuming you are a sophomore or junior), what your test scores are (SAT, ACT, SAT subject tests--if they still do those) (AP tests?), what those extra-curriculars are, etc.
Also check out collegeconfidential.com, which seemed to be big in my day.
You want to have a few choices at hand, so you have a back-up plan, not necessarily only of lower-tier but a back-up plan for an alternative "most prestigious private school" since even, with all else being equal, of top qualifications, you can get rejected for spurious/erroneous reasons.
What's really important, when applying to individual schools to be extremely focused--you've got to sell to them why you would be a good fit for them, and why they would be a good fit for you. In my high school class and those one to three years above and below me, tons of unextraordinary people and people with inferior track credentials to you got into just about every Ivy League, small liberal arts college and technical college you could think of. A good spread. Some of them clearly had some legacy/heritage (whatever it's called) points working to their advantage. But I think some of them did a good job of focusing and selling themselves to a particular school.
The grades thing is really going to hurt you--the sad truth and one of the things I loathe most and find the most counterproductive and stupid, in our educational system. Boring people with 4.0 GPAs and cliche, faux writerly written statements will most of the time (at least in my day) pass over the brilliant people who have inferior GPAs. Colleges very much also want obedient students, to perpetuate the tuition-mill and academic machinery, as much as they want brilliant superstars.
It seemed a decade ago that some of the Ivy Leagues and prestigious small liberal arts colleges weren't as hard to get into as you would imagine (see aforementioned success stories of unextraordinary people--I could list reasons why some of them were unextraordinary, from falling for ponzi schemes/multi-level marketing schemes, etc. to other horror stories I gotta recall from long suppressed memory).
It seemed to me (though probably wrong or outdated now) that UChicago, Carnegie Mellon and Cooper Union were a little more difficult to get into than the elite school average.
Talking to family and friends, and your school's guidance counseling office, might help in terms of getting an idea of what the past admission success of alumnis of your school and peers of yours, were, to different schools and generally, what sort of person has good shots at different schools.
Like Bad Wigins quipped, minority status or other canonical categories of "special class," underserved categories, etc. does get you bonus points.
Athletics will help but the requirement is that you get the attention of the school's recruiters in your sport, in a significant enough way to influence the admissions office. So when you've got the schools you're interested in focused, you gotta do what you gotta do to get the catalyzing attention. If you've got to take the iniative, then do it; if you got to play hard to get, then do it. If someone with insider information tells you that sport's coaches don't have much sway with the admissions office, then, so be it.
Prestige of a school is not just something to get off about on a forum, but a practical thing to consider for your life plans. Prestige is also what you do with it and depends on what you plan to do after graduating and getting your B.A./B.S., etc.
Rich, poor, Ivy League or state school, we all gotta do some of the same things. Keep up the fundamentals of our life, brush our teeth and floss, drive a car and follow traffic rules. If you've got a weakest link, then the prestige of your school won't even matter (who knows what that is--personal fulfillment issues, social issues, weight gain, etc. etc. etc.).