Scott Adams, of Dilbert fame, lists seven strategies for making people sound stupid:
If you are new to the Internet, allow me to explain how to debate in this medium. When one person makes any kind of statement, all you need to do is apply one of these methods to make it sound stupid. Then go on the offensive.
As someone who used to spend lots of time lurking on Slashdot and Usenet, I’ve got to say that Scott’s nailed it.