Another point is to be aware of "feedback", the annoying, howling sound that occurs when previously amplified sound is fed again through the microphone system. It usually is caused by setting the microphone implication level too high, or having a loudspeaker too close to the microphone or too directly behind it. When it occurs, you should not ignore it. Try first to reduce it by stopping speaking for a moment and moving back from the microphone before starting again. If it continues, try turning off the microphone or covering it with your hand until the feedback resides.