Get Your Students Hired
I usually have a "sit down" with all new students on a daily basis for the first 5 days of a new class. This allows us to get to know each other and this is when I reinforce the importance of participating in class and online as well. I remind them that the discussion questions online are not only a graded assignment but also a great way to participate in class.
Small talk gets the ball rolling. Even if it's off topic, there's usually a convoluted way to steer the conversation to the topic at hand. If not, at least it breaks the ice.