Position the Mic to avoid popping your plosives!
Put your hand an inch from your mouth and say “bumblebee”. The vibration you feel in your hand is caused by the breath you use to pronounce the “B” sound (“B” and “P” are plosive consonants). If there was a microphone instead of your hand in front of your mouth, that intense vibration would be picked up by the mic as a loud thumping sound. The way to avoid this when using a microphone is to orient the microphone about 5 inches below your mouth and at least 5 inches away. Try it by dropping your hand 5 inches and saying “bumblebee” again (see, no vibration! )
Keep the Mic close enough
Microphones, just like your ear, pick up less of your voice when you get further away. When that happens, a sound person has to compensate by increasing the volume on the mixing board. This causes two problems: First, background noises and mic handling noises get amplified along with your voice. Second, the chances of feedback go up when the volume level is increased. Try to keep the mic within 12 inches of your mouth for public speaking purposes.
Avoid pointing a microphone at PA speakers.
Speaking of feedback, the other way to increase the chances of feedback is to point the microphone at a speaker. Try to avoid this. If you do get feedback, point the mic away from the speakers, or even at the floor briefly (carpet can diffuse the feedback sound).
Make sure the mic is on!
It is always good to check ahead of time to ensure the mic is ready to go. Most mics have a switch that must be turned on for the mic to pick up your voice. Some mics have batteries – make sure they are fresh, and have a spare on hand just in case.
Specifics of different mics
Make sure to adjust the mic position ahead of time so you can stand comfortably at the podium with the mic in perfect position.
Avoid tapping or bumping the podium while speaking as this will get picked up by the microphone.
Handheld Wireless Mic
Pay extra attention to mic position with handheld mics because it is so easy to move the mic out of the ideal position.
Avoid clothing noise: make sure to clip the mic solidly where it will not brush up against clothing frills, hair or jewelry as you speak.