Fellow speaker,
Build your connection with your audience one person at a time: this is called "working the room." Talk directly to one person in the audience, to get their thoughts, ask them a question, or for some other reason. This gets everyone else to pay attention, since they want to be aware in case they are the next person called on.
Calling,
Tim Wilson
Professional Speech Coach
Free speaking tips at http://speakingquicktips.blogspot.com