As a technology instructor I get a lot of "center stage students" who are excited about the industry. I like the "observer" strategy, but I am concerned that the student might be insulted by this kind of singling-out. One thing that has helped me from time to time is having a brief 'current events' discussion at the beginning of class. Not only does this give late students a chance to arrive in time to receive the entire lecture (no dodging my lessons!), it also gives me a chance to work the excitement down a notch so we can focus on some detail work. The only drawback of this approach is that it can sometimes be difficult to stop a discussion that runs too long, but experience has yielded a number of tricks here, such as bringing up the discussion again after class is over, giving them a chance to stay after and discuss it some more of they wish.