Have you ever gone to a training or workshop where the speaker makes the assumption that no one knows anything and that everyone in the room is a blank slate? Get some background on the company, the culture, the level of experience with your topic, the event you're part of, the demographics of the attendees, and basics like how many people will be there (I use a SurveyMonkey questionnaire for this so it can be completed easily online). I imagine that those of you who read a lot of speaking blogs, books and newsletters tune out when you see this phrase, "know your audience." We