Here are some basic tips from a Professional Voice coach that may help you to improve your vocal delivery.
Before giving your presentation:
Be well prepared and rehearsed - write out your text in full, reduce to note format,
Rehearse your speech aloud making eye contact with your audience.
Look after vour voice! - Drink plenty of water the night before - avoid red wine cheese and anything with caffeine.
On the day:
Remember to breathe - in a pressured situation, the untrained voice can become constricted, and the breathing shallow.
Find your balance - knees unlocked, head up and shoulders released down.
TBS sequence - think, breathe, and speak!
New Thought, New Pitch - vary your pitch to convey a new point or message