Long gone are the days of the well-rounded student. You may have been one yourself... a member of two or three sports teams, a musical or two, band, youth group, camp counselor. You get the idea; you did a little bit of a lot of things. You were very well-rounded. Colleges like that, right?
Colleges now want a well-rounded class, made up of what I call "pointy" students.
When your kid does a lot of activities, it doesn't tell the admissions committee much about them. It doesn't tell them who they are, and what they will contribute to the campus. They are left wondering "What is really important to him or her?"
Help your teen really get involved in what is important to them. Do they love music? Maybe they are in a band, compose music, and write a music review column for the student paper. This will be more compelling to an admissions officer than someone who is in band, volunteers at the humane society, and works at McDonalds. Can you see the difference? All of those things are worthy pursuits, but the kid who goes deep into music tells a better story about who he is and what is important to him.
Of course the pursuits of your teen must be authentic. It's hard to uphold a fascade about being passionate about something if they're not. Don't push them to do activities that aren't part of who they are, just because it will look good on a college application. The whole point is to let your teen be themselves, and let that shine through. Let your teen explore what's interesting to them. They may start off on one path, and as they go it veers them into something else entirely. That can be a great story to be told.
Let me give you an example: Who is a college admissions officer going to remember more vividly when discussing applicants: the high school student who was in honor society, orchestra, competed in the science fair, and played tennis and soccer? Or the student who played hockey, was captain of his team, created a tradition of having Friday night pizzas, developed his own dough recipe, and started selling his dough to donate the profits to local hockey organization that helped procure equipment for under-privileged kids?
The first kid is well-rounded, involved in a lot of activities, and may have great grades and test scores to back it up. But does the college have any idea what is important to them? Any idea of who they are? Not really. But the hockey kid - he delved deep, and took his passion and did something with it.
This isn't to say your kid has to start a foundation or deworm orphans in Somalia (thanks, Legally Blonde). But let your teen direct what they are interested in, and encourage them to follow those interests.
Let them go deep, rather than broad. Let them do what they love and be memorable for it.