programming to create leaders

I just had a quick hallway conversation about student ministry leadership programming with our Student Ministry Team Leader. So I was wondering, what really works? What transforms a regular student into a student leader?Is it a depth of knowledge (I'm guessing not)? Is is requiring them to serve (might work for some)? What needs to be in the mix? How can you engage students that honestly were already great leaders over in the children's wing as kids while also picking up emerging leaders from new high school students who are just starting to engage? What process will challenge and inspire students to become leaders?