For each activity, give a concise, two-sentence description of the actitivity and, more important, your involvement in it. Always put a positive spin on your involvement, even if it has been limited. This coming fall, for instance, I'm keen to find some choral soloists, especially sopranos and tenors. And we could surely use more cub reporters for the school paper. I didn't need these as much last year, and may not next year.
Applicants are wise to ask about such particular needs.
Leadership skills are undoubtedly important and desirable, but not everyone can be a campus leader at the same time, nor should everyone want this occur. Only after you've passed the first hurdle of presenting an academic history that predicts academic success in the college's curriculum. If that is not taken care of, all the offices and extracurricular accomplishments are moot. Once you've passed the 'academically admissible' review, then involvements can help you. All selective schools want a well-rounded student body, but not made up of the exactly the same type of student.