These basics apply whether you use a headset, podium mic, or handheld:

• Distance — keep a consistent distance from the mic. Moving closer creates a boomy bass effect (proximity effect); moving away creates thin, distant sound
• Angle — speak slightly off-axis rather than directly into the mic to reduce plosives (popping on P and B sounds)
• Volume — speak well below your unamplified level. The mic does the work; you provide the nuance
• Handling noise — hold handheld mics firmly without squeezing. Movement and fidgeting create noise the audience hears