I've found it's always good to have some kind of agenda. It doesn't have to be very structured--you can say the group will talk about job offers first, then about current jobs and any problems members may be having with them, perhaps. That way you can make sure you get through all the important topics in a timely manner, in case anyone there cannot stay long.

That could be your responsibility, or the leader's, or whoever else wants to do it. It sort of depends on what kind of management you have.