I second all the above. Also, if you get nervous about doing the open mic, keep this in mind. If you live in a tiny town where nothing's open at night, then there are sure to be people there who are bored out of their minds and starving for stimulation.

I don't want to sound like a preacher, but this especially includes young people who are apt to get into trouble (like drinking) because there's nothing else to do.

But by playing at the coffee house, you will be providing interesting music, you might give somebody else the idea of taking up an instrument, and you will give your neighbors further reason to get out of the house and perhaps make new friends.

So if you get nervous, say to yourself over and over, "This is not about me, this is something I am doing for other people." It helps.