I actually figured out how to do this...push and hold the '#' button while entering text. It will take you to a symbol menu that you can scroll through with a bunch of other symbols.

Hello,

I am trying to enter an email address for a contact, and that email address contains an underscore character. I can't seem to figure out how to enter an underscore character. The manual doesn't show it in the list of symbols. Any ideas?

Thanks.