Writing Excuses

The Writing Excuses team sits down to talk about religion as a world-building device: your characters probably believe in something, so what is it? How does it affect their lives? How does it change their thoughts and motivations (and swear words)? And when you're developing a fake religion, how do you avoid religious bias and keep from offending people? Is it best to develop something completely new, or make a few changes to a real Earth religion?