Delivering effective oral presentations involves three components: what you say (verbal), how you say it with your voice (vocal), and everything the audience can see about you (visual). Verbally (and as a general rule), do not write down and memorize or read your full text, because then your presentation will sound like what it is: a recited written text. Instead, memorize the outline of your presentation — that is, a tree structure of main points and subpoints — and speak ex tempore, reinventing the words as you go along. As you do, you will occasionally need to think about what to say next and find the most appropriate words to say it. Instead of using filler words (um, er, you know, I mean, etc.), simply pause. If you say um, you get about half a second of thinking time and the audience is likely to notice the um and be irritated by it. If you keep silent, you can get up to two or three seconds of thinking time without the audience noticing anything. Even if attendees do notice th...