How to be a great leader

We have all changed someone's life -- usually without even realizing it. In this funny talk, Drew Dudley calls on all of us to celebrate leadership as the everyday act of improving each other's lives.

The world is full of leadership programs, but the best way to learn how to lead might be right under your nose. In this clear, candid talk, Roselinde Torres describes 25 years observing truly great leaders at work, and shares the three simple but crucial questions would-be company chiefs need to ask to thrive in the future.

Economics writer Tim Harford studies complex systems -- and finds a surprising link among the successful ones: they were built through trial and error. In this sparkling talk from TEDGlobal 2011, he asks us to embrace our randomness and start making better mistakes.

David Logan talks about the five kinds of tribes that humans naturally form -- in schools, workplaces, even the driver's license bureau. By understanding our shared tribal tendencies, we can help lead each other to become better individuals.

Four-star general Stanley McChrystal shares what he learned about leadership over his decades in the military. How can you build a sense of shared purpose among people of many ages and skill sets? By listening and learning -- and addressing the possibility of failure.

We each want to live a life of purpose, but where to start? In this luminous, wide-ranging talk, Jacqueline Novogratz introduces us to people she's met in her work in "patient capital" -- people who have immersed themselves in a cause, a community, a passion for justice. These human stories carry powerful moments of inspiration.

With help from some surprising footage, Derek Sivers explains how movements really get started. (Hint: it takes two.)

Facebook COO Sheryl Sandberg looks at why a smaller percentage of women than men reach the top of their professions -- and offers 3 powerful pieces of advice to women aiming for the C-suite.