A lot of the users of the internet don't take too kindly to new people on the internet, who are just wandering around taking their first steps in the virtual world, such as it has been refered to. It seems they have one main rule over all others though... "Never suffer fools gladly." While it may never be stated out loud, this is the very crux of netiquette.
When you start on any newsgroup it is considered polite to introduce yourself. The opposite is true for chatting. If you introduce yourself and let people know you're new then they tend to look down on you and start picking on you, trying to provoke a response. I always found that agreeing with them, regardless of what they say, has a tendancy to diffuse any possible trouble.
Most chat areas are can be best described as parties(they've just been going for a hell of a long time....). When you go to a party where you don't know anyone, you have too options. get involved or just sit in the corner and look moody. Have you ever gone into a party and, within five minutes, shouted at everybody for not talking to you? No. What you do is listen in on another conversation and throw in your own two cents worth. Same on chat channels.
If no one seems to be talking about something you're interested, it is no crime to offer up a new topic of conversation. Just be aware that you might get some negative responses and might find yourself trying to defend yourself and your choices.
Newsgroups are different from chats in that they tend to be able to stick to the topic a little bit better... a little bit. And it's because they take the topic seriously you can get yourself into real trouble. It's a good idea to have a general knowledge of the topic they're talking about and taking the time out to think about what you write before you send in a note.
Nothing is more likly to set of a newsgroup quicker than sending in a question for them that has been asked umpteen million times before you did. Possibly the best message you could send first is a request for the FAQ list. Frequently Asked Questions are compiled by various newsgroups so as to inform new people (and some of the old ones for that matter) of the general topics that have been discussed to death before. This allows the "newbies" to intergrate easier with the "oldbies" and ease tension.(nothing worse than gettin on a newsgroup and finding half the messages are flames.)
Flaming is a grand old tradition on the 'net. Basiclly the minute someone makes a mistake they are sent messages of ridicule, abuse and derogatory statements as to their mothers night time activites. Can be fun if you're on the right side. However, some people have begun to sue over comments made on newgroups, so, again, becareful what you say.