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:

  1. Critical Judgment
  2. Critical Judgment II

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.