Netiquette varies from domain to domain
What’s perfectly acceptable in one area may be dreadfully rude in another. For example, in most TV discussion groups, passing on idle gossip is perfectly permissible. But throwing around unsubstantiated rumors in a journalists’ mailing list will make you very unpopular there.
And because Netiquette is different in different places, it’s important to know where you are. Thus the next corollary:
Lurk before you leap
When you enter a domain of cyberspace that’s new to you, take a look around. Spend a while listening to the chat or reading the archives. Get a sense of how the people who are already there act. Then go ahead and participate.