Learn to be a good follower and team player first. Listen, respect others, commit to the team goal.
Watch those who lead, figure out what they do that makes you feel valued, motivated and willing to work hard for the team goal - also observe those who lead who make you feel beaten down, undervalued and uninspired, and DON'T emulate them!
Ok, that's philosophical stuff, I think you are asking for what kinds of things you can do to demonstrate those qualities for admissions purposes. I suggest reading the posts where appointees have posted their stats and activities - there will be a wide range there. There are also some threads over the last few years that address your question.
In general, I think it's better to go for quality over quantity, don't spread yourself too thin, but choose some good substantive activities where you take an elected role or project oversight role that demonstrates your ability to organize people, resources and plans to meet a goal.