Jeffrey,
Can you be more specific? What kinds of things are you doing now and what kind of content are you teaching? Specifically in discussions or assignments. As a general statement I would say that you should "motivate" them with assignments that connect with them. Give enough flexibility in assignments that students can express their individual interests. For example, don't assign everyone the same exact website to create in a web development class. Provide the assignment framework and expectations, but the type of site they create is up to them. Open it up - make sure you are using multiple mediums to connect with the diversity of student learning styles.
Herbert Brown III