Check the pronunciation of difficult, unusual, or foreign words beforehand. Use your voice to communicate clearly Speak loudly enough for everyone in the room to hear you. This may feel uncomfortably loud at first, but if people can't hear you, they won't listen. Speak slowly and clearly. Speaking fast doesn't make you seem smarter, it will only make it harder for other people to understand you.
Key words are important.
Speak them out slowly and loudly. Vary your voice quality. When you begin a new point, use a higher pitch and volume. Slow down for key points. Stand straight and comfortably.