1. First: don't bore the listener with too much extrapolation and meandering... you can freestyle it somewhat but it is indeed best to work from a script. 
2. Mentally set the stage. Really picture a specific person to whom you will talk. This will help you not sound numb or artificially passionate in your delivery.
3. Now mentally picture the person's face reacting so that you know you got through. Ask yourself what kind of vocal sound - tone, inflection, pace, volume, articulation - you need to use to get that response. Use that! 
4. Watch your speed of delivery. Don't neglect the natural pauses and moment of silence needed by the listener to digest what you say. Give yourself permission to breathe.
5. To keep an open throat and ribcage for good resonance and breath, do not slump or stiffen your spine. Park your head over your tailbone.
6. USE YOUR EYES and HANDS when you're speaking, as you would if the object of your message was in your gaze. This can make a HUGE difference. Try an experiment... quote some passage with dead eyes and still hands, then speak it again with active eyes, brows and hands. You'll be a believer.
7. Don't fake it. Use tone colors that are authentic to the meaning of the words coming out of your face! 
8. Use good breath technique... 'Pull' your speaking voice as well as you do your singing voice to balance breath support and control. Power your voice from your pelvic floor.
9. If you are responsible for the final recording, edit your file with software such as Audacity to get superfluous er, eh, sputter, false starts out.
10. Picture your audience naked. No, actually DON'T, that doesn't help at all (who starts these things? :)

Labels: audacity software, Judy Rodman, Speaking Voice, teleseminar, voice over