-Do weird things every day.
-Change up your routine.
-Watch things/talk about things that are interesting to you. Show your outside-of-class interests.
-Get students talking to each other.
-Get students creating.
-Get students to explicitly connect your class to things happening in the outside world.
-Let the class be loud sometimes.
This, of course, is an incomplete list. I guess it all comes down to making connections, both academic AND interpersonal-- and letting those little moments of creativity and light guide your approach to the class.