When asked to give a talk, be sure you take control of the environment. The audio system is your lifeblood to the audience. By this I mean TEST the microphone / loudspeaker system. Not just bellowing “1-2-3.” Put on the head device, or clip on the lapel mic or hold the 10 inch mic in your hand. I really prefer the over the head kind – like Madonna made popular.
Hake sure the engineer tells you how far to hold these. Speak as you would during your talk. Don’t tell him “I have a booming voice – I don’t need a mic.” You do. There will be people in the audience that are hard of hearing. Many may ask to record your talk and you’ll need to have it come out crisp.
Another tip – when you turn your head to talk, you may lose the maximum connectivity to the system. This is really true with lapel mics. If you use a slide changer AND a laser pointer AND a hand-held, you either need to grow a new hand or learn to manage all three. I jam my bright green laser pointer next to the clicker (I do not like the wimpy red lasers on slide clickers), so they hold as one unit.