It is an important device for gaining attention. If you suddenly stop in midsentence, students will look up from their notes to see what happened. Planned pauses also give you and your audience a short rest. Some faculty take a sip of coffee or water after they say something they want students to stop and think about. Watch out for vocalized pauses.
Silent pauses are more effective.
Adopt a natural speaking stance. Balance yourself on both feet with your toes and heels on the ground. Beware of shifting movements or unconscious rocking to and from. Keep your knees slightly relaxed. Shoulders should be down and loose, with elbows cocked, and your hands at waist level.