Mention Community Values!
How do you make CommunityExpectation known? Some channels try to inform newcomers about basic community expectations via a "welcome" message, others use the channel topic to link to a FAQ somewhere on the web.
Here is an example of a "welcome" message that explains the basic netiquette: Don't paste, and don't ask silly questions like "Can I ask you something?"
-ChanServ- [#perl] Don't ask to ask, just ask, preferably
politely. If you're in luck, the genie might
answer. If the need to paste is overwhelming try
perlpaste at http://dragon.cbi.tamucc.edu:8080
But that doesn't cover real values -- that's just basic etiquette. What is important, is to act as a RoleModel: If discussion on #emacs is enthusiastically off-topic, it makes no sense to reprimand users. When a newbie does ask an Emacs related question, be sure to react to it, however. Even if you don't know the answer, the point is to show all users and the person asking the question that people care. We want to help.
Here's another example of how to repeat community values: If you find an old question in a backlog full of off-topic fun, and you know the answer to the question, don't just answer the question. First, ask back: "Has anybody answered your question, yet?" If the answer is "no", then go through the basic moves: Let the user repost his question, etc. The important part was to remind the community that answering Emacs questions still is the main topic of #emacs.