My students have reacted very positively to being recognized as leaders. It is pretty exciting to see enthusiasm in serving as a helpful hand around the class.
In my room I have a system for students that serve as leaders. Sometimes being a leader is as simple as serving as a role model by doing what you're supposed to do, when you're supposed to do it.
Other times, I ask students to complete a task to help class run more smoothly:
class materials distribution
focusing the projector
turning lights on/off
parking projector cart
I sometimes ask leaders to complete written assignments to help me keep class interesting for my students. One of my first written simple leader assignments was a poll asking what their favorite songs were.
I give students that have been asked to be leaders an opportunity to sign the leadership log. At the end of grading periods, I reward students that have served as leaders. To discretely tell a leader that I appreciate their leadership, I give them a pass to the leader station. They will then sign the log, complete the assignment (if there is one that day), and rejoin class.