Experienced speakers generally devote the first half or two-thirds
of a presentation to a careful introduction of the topic and save the
highly technical material for the last few minutes. In this way, the
beginners can under stand a significant part of the presentation, and
the experts will learn some of the fine points. Most importantly,
everyone will end up respecting the speaker as an authority on the
subject who is also attuned to the audience and respectful of the
varied needs of those in it. I am also appreciative of speakers who
summarize at the very end the key points they’d like me to
remember. That way, if I’ve dozed through part of the talk or just
failed to understand it, I at least walk out of the room with the major
ideas reverberating in my head.