If in doubt do a sound check ahead of time. The human voice can easily overdrive the microphone range. Be sure persons in the audience use mikes if a remote site must hear them. Try to relax, remain open and friendly. Smile as often as you can.
Cameras tend to turn perfectly personable presenters into robots.
Watch yourself in the mirror to rehearse or practice with a home video camera. Ask for a recording of the program to critique yourself. Slow your movements slightly for the camera. Speed seems exaggerated when viewed on a television monitor. If demonstrating or holding an object for the camera, hold it still and turn it slowly.