All instructors need to demonstrate good leadership skills. You have a large variety of methods at your disposal for maintaining your students attention. Bear in mind, most of your students will be following your action for better or worse. As a leader, pay close attention to your actions, gear, and especially judgment. Make certain you practice skills in a suitable environment. If conditions are too bad, like Hurricane Irene - call off the class as safety is paramount. Most of the time, you can divert to an alternate location - perhaps a more protected area or smaller stream. the ACA has two excellent articles on judgment:
Another consideration is setting up teams for group activities. In larger classes, we will sometimes break the class into smaller more manageable groups provided we have adequate co-instructors. This can be fun when leading a trip, providing different levels of challenge, learning how to work together - perhaps on simple rescues. Here is an interesting article on this topic: Group Dynamics & Team Building.