Milliways has existed for a very long time and its regular users include members both past and present, as such there is a sense of community, and like any community a number of rules of etiquette have formed over the years.
The denizens of Milliways are usually polite and helpful to strangers and newcomers, but do expect those that wish to hang around to familiarise themselves with "the way things are" and play nice. As with most communities, newcomers need to show respect for the existing members and not expect the community to immediately adapt to accommodate them.
So the following is an attempt to describe some of the more usual pitfalls that a new user may come across.
Milliways is a relaxed and informal environment, and as such there is often a lot of joking and messing around, a part of this that a newcomer may find difficult at first is the way that users will often ridicule and criticise each other, themselves, and anything else that catches their attention. If you happen to become the target of such comments then do not take it as a personal attack, it usually isn't.
Users are expected to express themselves using full and valid English sentences and words, the use of "txt spk" is not tolerated, and any bad spellings, abbreviations, and general bad use of English will typically result in corrections being offered, or scorn poured upon, as appropriate. Not only does proper use of English allow you to make yourself better understood, but it is good practice in preparation for the Real World (and "txt spk" really isn't any quicker than real English if you are practiced).
Meta-Questions aka Ask or Ask Not, there is no "May I"
If you have a question or something that you require help on, just come straight out and ask it, be as specific as you can, no asking "can I ask a question?". Ask the actual question and anybody that is able and willing to help will do so, if you get no answer its because nobody can help you. Don't repeatedly ask the same question if no one is replying - if someone was able to help they would do, asking them over and over will just annoy and reduce the chance of someone helping in future.
Don't assume people know exactly what you are talking about just because your question is obvious in the context of your specific course. For example, a programming question like "how do I do $foo" is less helpful than "how do I do $foo in $language". The former is likely to get you answers covering C, Python, Haskell, etc. rather than the language you are interested in.
Flooding the Channel
If you have anything that you wish to share with the world (for criticism generally ;) that is more than a line or two of text then you should make use of the SUCS website utilities of ShortURI and PasteBin as appropriate, and just paste the resulting url instead. this saves cluttering up the screens of all of the users. In the case of questions on items of coursework it would be a good idea only to paste the section around the actual problem, not your entire answer, as anybody can see the result.
Eric Raymond maintains quite a good (but long) document on how to ask questions in a technical forum. It is worth a read if you have time: http://www.catb.org/~esr/faqs/smart-questions.html