Microphones are like audio flashlights
A Microphone functions like a flashlight, but for sound. Much as a flashlight will light what you point it at, a microphone will 'hear' whatever it is pointed at.
Proximity Effect
The closer you get to the capsule (diaphragm) of the microphone the fuller and richer your voice will sound. Speak directly into the mic! 2 - 4" is great. You of course can bring the mic closer, but be mindful that the further away the mic is the harder it is for it to 'hear' you.
Holding the Microphone
No 'cupping' or covering the ball end of the mic. This will result in a muffled sound and can create feedback. Mics have handles for a reason!
Mind the Antenna!
For wireless mics (Handhelds), avoid gripping the base of the mic as well, this is where the transmitter (antenna) is, and covering it can result in 'dropouts' or loss of audio.
Lectern Mics
Don't be afraid to adjust the mic to meet your needs, no-one will hear you if the mic is above your head or well below your chin. Normally these mics have flexible 'goosenecks' or are on an adjustable stand. An example of good technique can be seen below.
