I think students motivation should be cultivated with time and instructors should proceed by steps: motivators should fix some personal objectives during the course, in order to construct their proper way to bring out the best they can from the classroom.
When students reach a sufficient level of autonomy, security and interest in what they are learning, motivators should give rewards, such as more activities in groups, extra debates on particular topics, give students a chance to research individually on some topics, to relate to the class what they find out etc.
This can increase self-confidence, curiosity and a good relationship between instructor and student. This could be very interesting for growing an open-minded way of thinking and a higher level of learning. It could be a good method to stimulate and inspire students to research and keep on exploring, during the course, and during their life.