Using a wireless lapel microphone is the best way to pick up a couple’s vows when you’re videotaping a wedding ceremony. Place the transmitter in the interior pocket of the groom’s suit jacket, and clip the mic on his lapel.
I suggest putting the mic on the groom because it will generally blend in better with his suit than it will with the bride’s dress. And because they are standing so close to each other, it should pick up the voices of both. If you‘re shooting a wedding with two brides, or with a groom who doesn’t want to wear a mic, see if you can put a wireless lapel microphone on the officiant.
Place the lapel mic as soon as you arrive at the ceremony, and test it to make sure it works. I like to leave the transmitter part of the wireless microphone on (the part that the groom’s wearing), and then turn on the receiver (the part hooked to the camera) only when the ceremony is about to start.
If you turn on both parts well before the ceremony, be sure to warn the groom. He needs to know that you will be able to hear (and might record!) any nervous comments or last minute trips to the bathroom.
Also, be sure to find out if there is a wireless microphone system in use in the church. If so, check that your mics are not using the same frequency. If they are, you could run into problems and get some ugly feedback.