When you are speaking at an event that has multiple speakers,try to listen to as many of the other speakers as you can. In particular, don't miss the keynote or general session speakers. By doing this you are able to add a polish to your talk and to the event as a whole. It also might save you some embarrassment.
I'll never forget many years ago I was doing a breakout session fora big real estate company. We then went to the closing general session an hour later, the big shot keynote speaker made a fool of himself by using material I had gone over already. People were looking at me and winking. There were only two concurrent sessions going on and it would have been really easy for the keynoter to stop by and check out the breakouts, or at least find out what I and the other breakout session speaker were going to be talking about. Besides listening to as many speakers as you can, make sure your material is really unique which will help guard you from embarrassing situations.