I would mention that this is one of the least mentioned Moodle tricks, but definitely the most helpful if you’re managing a large class with multiple sections.
It’s possible (and quite easy) to set an enrollment key for a group that is different from the enrollment key of the course. Students who use the group key will be entered into both your course and their group at the same time. Thus, you get enrollment and grouping all in the same single step. (http://patrickmalley.com/2010/02/11/course-to-class/)
If you happen to be looking for great themes, Patrick is the guy to visit online. Newschoollearning.com has loads of free themes for Moodle installations (and a good price for some of the prettiest custom themes on the net.