+ What's it about? + Do you know your material? + How long is it for? + Are you explaining, lecturing? + What is the style? If you know more about it than

+ What's it about? + Do you know your material? + How long is it for? + Are you explaining, lecturing? + What is the style? If you know more about it than the audience, then say up front that you expect everyone in the audience to know more than you about various bits, and that you're simply there to share something on which you have some expertise. Starting with that tends to put an audience on your side, and emphasises that you acknowledge their expertise. Depending on your answers to the questions, though, this might not be appropriate, but without more to go on I can offer no other advice. Just for reference, I regularly speak to audiences of up to 500, and have several times spoken to audiences of up to 2000 and done live television.