Yogi Berra once said, “You can observe a lot just by watching.” Observing an audience before you speak can really help gauge the attitude and atmosphere of the situation.
First, if the front rows are filled, you can usually anticipate an enthusiastic audience; if not, you may have to spend time in the opening creating a positive attitude about you and the topic.
Second, if you arrived as they just finished eating, observe if they had a heavy dessert such as cheesecake or apple pie. If so, you may have a lethargic group initially. Generate enthusiasm in your opening to wake them back up.
Third, if the audience is divided into cliques according to department or occupation, there will be challenges in uniting the group to respond to you instead of each other. If people do not know each other well (you can usually tell this by the amount of laughter and talking going on among the tables or rows), you will have an easier time in getting the audience to act as one in responding to your message.
Fourth, if the chair or introducer has a rough time settling the audience down for your speech, you will need to work harder at getting their attention and keeping it since they are easily distracted and may be pretty high strung.
Finally, seek a sense of the level of formality of the group. Because of the casual way they are dressed, or the easy manner the group seems to have sitting in chairs or at tables, you may be more informal in your language; perhaps you would take off a jacket or feel more comfortable moving into the audience at special times in your presentation.
Certainly, you want to do a thorough job in evaluating and analyzing your audience before you arrive at your speaking location. However, being a careful observer before you speak can help adapt even more specifically as you deliver your presentation.