Andy Doctoroff interviews applicants for Harvard, and he's got a good piece in the Huffington Post today, "Dear Eighth Grader: So You Want to Apply to Harvard? Some Words of Advice…"
The central message is that good grades, high test scores, and impressive activities alone aren’t what impress him during an interview. “Intellectual ambition, drive and zest for discovery” are, especially when they’re genuine, not just being forcefully presented in an effort to get into Harvard.
And make sure you don’t miss this part near the end (and remember, this is a guy who went to Harvard).
Frankly, it's not really that important whether you go to Harvard. There are a lot of Harvard graduates who do not lead productive lives. And, of course, Harvard and other comparable schools have not cornered the market on success."