“Is there a lawyer in the house?”
A team was making a presentation at the IBC (International Business Challenge) competition a few years ago. At one point there was a legal issue in the case and obviously, since they were not law students, they didn’t have an answer to a question a judge asked. One of the presenters jokingly said: “Is there a lawyer in the house?” The head judge looked surprised, looked around, rolled his eyes and said: “Hello!” Little did they know, the head judge WAS a lawyer!
Fact is, these students knew the judge’s name beforehand and they had access to Google. Had they taken 5 minutes to look him up, they would have known he was a lawyer. That situation would have been MUCH smoother had he said (with a smile): “Well, we understand that you’re a lawyer, can you tell us if this is illegal?”
Knowing your audience is crucial in any communication whether it is written or verbal. If you’ll be speaking to a large audience try and find out general demographics such as: age, gender, field of work, interests, etc. If you have specific people in the audience you have to pay special attention to (e.g. judges, potential employers, hot women, professors, etc.) see if you can get their names beforehand to get some background information. If you are only presenting to one person MAKE SURE you look them up and try and find out anything you can about them. If you can manage to squeeze in things that show you did your homework, it’s usually quite impressive! 
Being aware of your audience’s characteristics will allow you to tailor your message and/or delivery to suit them and you should be able to capture their attention long enough to get your message across…