Rehearsal is preparation time devoted to the most crucial and difficult parts of the presentation while simulating the actual speaking conditions as closely as possible.
Practice should not be going through the presentation time after time. Instead, rehearsal time should be spent on the opening and closing of the presentation, pacing and delivery, and smoothing out rough spots. Public speaking is much like flying a plane. Once the plane’s in the air, the flight is usually smooth and on “autopilot.” It’s getting the plane into the air and landing it that are the most difficult tasks. Therefore, most of your rehearsal time should be spent on getting your presentation “launch” and “landing”—the first 60-90 seconds and closing 2-3 sentences. Script out the opening and closing of the presentations to help prevent getting “tongue tied” during these crucial times. Practice smooth transitions from one slide to the next as well pauses, where appropriate, for dramatic effect. When rehearsing, simulate the actual speaking conditions or worst-case scenario you are likely to encounter as closely as possible. When a professional football team is going to be playing in a noisy domed stadium, they conduct some of their practices with a public address system blaring crowd noises at the same or higher decibel levels they are likely to encounter. Demonsthenes, the renowned Greek orator, overcame his inarticulate, stammering pronunciation by practicing with his mouth full of pebbles.