Anyone who is using twitter should consider this. Andy Piper has put together a list of rules for users of twitter that I think are bang-on. I try to follow them myself, and like Andy, I tend to drop people who break them often.
Besides Andy’s blog, you should also follow him on twitter: if you do, you will learn alot. Trust me.
P.S. BTW, he works for IBM, not Moo. I just thought I should point that out. 🙂