From a conversation with an adcomm member I learned that (at his school) one gets points for the intensity of the leadership experiences listed. Here are some examples of activities I've learned of on SDN and how I'd rank them (opinions, as always, may vary). Multiple experiences increase the score. Ponger and CombatMedic172 would obviously get the highest points. They are very unusual, and few would come close to what they've accomplished. It's OK to shine in another area if leadership isn't your forte.
Level I: 1) President of a club for a year. Led meetings. 2) Start small, common-interest club eg card playing, sport, WOW players. 3) Lead boyscouts in completing badge requirements. 4) Initiate food drive among your friends and collect donations for a food pantry. 5) Member of student senate.
Level II: 1) Club officer multiple years, eventually president. 2) Start new club attracting 20+ members to do community service, or arranging speakers, or to successfully campaign for a change on campus. 3) Shift supervisor or trainer of new employees.
Level III: 1) Board member for health-related organization or charitable foundation for several years who helps organize/participate in health fairs, involved in presentations to get funding for projects, brings opinions to the meetings and campaigns to effect change. 2) President of three clubs some of which do community service or raise money for projects. 3) Organize 3-4 charity concerts with large attendance coordinating multiple committees.
Level IV: 1) Chief Editor of school paper, writing editorials to sway opinion. Direct policy. 2) President of student senate. 3) NCO or officer in the armed forces who trained/led a team/unit in combat.
Level V: 1) Founded a charitable group, raised thousands of dollars for many projects, multiple year involvement, group continues after your departure. Branch groups started in other locations under your leadership. 2) Start a free clinic, recruit doctors, nurses, and student workers to volunteer their time. Raise the money for supplies/pharmaceuticals or get them donated. Help hundreds to thousands of patients in the time you're involved. 3) Start a successful company with 5+ employees and make a profit.