The kind of microphone you use—clip-on, hand-held, or podium-mounted—makes a big difference in your speaking dynamics.
A podium mic like this one would be my last choice—it ties you to one spot and forces you to swivel your head around the mic as you address different parts of the audience. It’s better than nothing, but it restricts your movement. I’d ask for something different.
If you’ll be using a hand-held mic, that’s better, because you control its position. Even so, you’ll want to practice with it. Some mics may be held a foot from your mouth. Others you practically have to “eat” to get amplification. In either case, you need to be conscious of where it’s pointed. If you swivel your head but don’t move the mic, then your voice will fade away and listeners will miss something. If you inadvertently point the mic at a sound speaker, the resulting feedback will disrupt your talk.
Lavalier or clip-on mics are probably best—once positioned, they stay positioned and give you hands-free movement. On the other hand, they generally require some cord pulling and adjusting to get you hooked up. A battery pack is required to transmit the signal, and this pack must be hooked onto a belt or a waist band. Most men don’t have to worry about that, but if you’re a woman, you’d better not plan to appear in a sheath dress. In either case, know how to switch the pack off when you leave the stage so you don’t inadvertently advertise a private conversation or—God forbid—a stop in the restroom.
Whatever you use, a sound check is mandatory. And when you are asked to do the mic check, just talk; don’t blow into the mic to see if it’s on. That’s an amateur move that can damage the mic and make enemies of the sound professionals you’re trying to work with.
It all goes back to one of the fundamental principles of speaking: rehearsal. Insist on rehearsing your talk with the very equipment you’ll be using in front of the audience, including the sound system. I’ve seen panel discussions ruined because of feedback squeals caused by the shortsighted refusal to rehearse. Those in charge tried changing the positions of the speakers, turning off one mic after another, and moving chairs around. When it was over, no one remembered a thing that was said. Don’t let that happen to you—rehearse!