Hi Robert, I think a good guest speaker provides a forum of providing both information s/he wants to provide, along with an informal, open opportunity for questions the students want to ask. Often, they will feel free to inquire about A-Z, where they might not be willing to in class, or are not informed enough to ask pertinent questions. Sometimes I will prompt the quest speaker to "make sure you mention such and such", as that help reinforce ideas I've been trying to convey, and hearing it from an outsider somehow brings a degree of additional credibility. Barry Westling