WAIT!!! While the answer Will gave is technically correct, it's not your best option.
This will TOTALLY SAVE YOUR ASS:
What you REALLY want to do is get a very inexpensive adapter from Radio Shack. This adapter is a Female XLR to Male XLR(x2) splitter. (In essence it allows you to plug your microphone into both mic inputs, sending your signal into both channels. It'll cost you about $5)
Now, set channel 1 to a level that works for your application. There are very formal ways of setting the volume, but just set it to a level where the audio levels (located under the XL1 handle) are full but not peaking out. Once that's set, take channel 2 and decrease the volume to 1/2 what channel 1 is at. (In reality, this will be acheived by adjusting the "balance" knob.) The general effect is that you'll always be recording a second channel of audio at a much lower level, that way, if someone yells or makes a loud noise and ruins the audio on channel 1, you're more likely to have usable audio on channel 2.
When you get to post-production, and any audio is blown out, just cut in channel 2 and see if that's better. Then, pan it all to center like Will said.
Please let me know if you have any more questions.
Cheers!
-Jim