How do you become a great moderator? Simple—with practice. Facilitating sessions is a learned skill that improves the more you do it. There are some simple tricks and techniques behind it...Jared Spool likens effective usability testing facilitation to playing 3 different roles in the course of a session: the flight attendant, the sportscaster and the scientist.
His analogy rings true for me and my experience of running usability sessions.
Moderating with Multiple Personalities: 3 Roles for Facilitating Usability Tests - article by Jared Spool