In a study at the Chinese University of Hong Kong's School of Education, more than 100 men and women were shown photographs of males and females, smiling and unsmiling. They were then asked to fill out a questionnaire giving their impression of each person pictured. The results showed that a smiling person was perceived to be more intelligent than an unsmiling one. A smile also relaxes you and makes your audience feel more comfortable. Keep a glass of water handy if speaking for more than 20 minutes.
Timing is also important.
Most speakers try to cover too much material both on their visuals and in their speech. One advantage to visuals is that you can gauge your presentation time by the number of visuals you have prepared. If your visuals are designed correctly, you can cover one visual approximately every one to two minutes. Therefore, if you have been asked to put together a 20-minute presentation and you have nine to 12 visuals, you will have 20 minutes of material. When someone asks you to speak, be sure to clarify how much total time you have.