Hello Rebecca and welcome to the Cow Audio Forum.
Good ideas from everyone so far.
Sometimes the house system audio is noisy and plugging in can result in a ground loop which results in a buzz. If you can live with the noise do that. Be aware that the operator may change the level and you may need to compensate for that in the moment. In a properly designed system, that won't happen, but you never can tell.
If that's the case (and you should get there early to hear what the system sounds like) you may want to setup another mic at the podium and grab clean audio.
Frequently the "line level" I am given from the house is somewhere between mic and line, forcing you to decide which setting (mic or line) to use on your camera. I try to get a sound check to figure out the best settings and use a mixer before the camera so I can more easily make adjustments if necessary.
I once attached a wireless lav to a podium mic on Capitol Hill because the house feed was pretty nasty. It worked, but you also have to be aware of cell phones that cut the range of the wireless. Putting the receiver as close as possible to the transmitter and cabling back to your audio input can help.
Do you need the audience questions? If so, how good does that audio need to be? Usually there are "runners", people with wireless mics who take the mic to the person asking the question. Will the question askers be on camera? If not, you may be able to get their sound from someone operating your boom mic to a separate channel or camera.
And, trust me on this, you will have to tell people to wait for the mic even if you announce ahead of time that you will be bringing a mic to the person with a question. A second plan would be to put a mic on a stand at the front of the audience and make people with questions come to the mic. Again, you WILL have to coach people to, "Please use the microphone!" because they will just start asking questions from their seat.
Regards,
Ty Ford
Cow Audio Forum Leader

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