Charlie Stross has an excellent writeup on doing readings.
I fear the day that I have to do a reading. I've never been a smooth talker in public settings. I've deliberately put myself in situations where I had to speak in public. In high school, I opted to take Public Speaking instead of the regular Speech class. It took me a couple tries to actually pass the class, but when I did I did so with an A. I've been a member of Toastmasters and I've run panels at Penguicon (some better than others).
It's strange. Despite the fact that I talk to people for work on a very regular basis, have stood up and spoken in front of groups of strangers on many occasions, I still stuffer from extreme anxiety at the thought of speaking in front of groups. The thought of reading something I wrote is downright terrifying. It won't stop me if/when the situation presents itself but I apologize in advance to those who end up suffering through it.