Guest Speakers - How to Make Sure They Go as Well as Possible

i'm wondering about how you go about making sure that your guest speaker a appearances go as well as possible. That was one of my favorite things to do, is to bring in people from the community into the class. And it was so important to me to do that, because then i would get to model my own learning. I think that was one of the most influential things i ever did as a teacher, for myself.