This guide was written to illustrate the proper way to communicate on an IRC network especially one of the more formal ones, like Freenode and OFTC where a lot of practices that may be tolerated on other IRC servers are either not tolerated or looked down on. Since these networks are home to a large number of open source projects (and thus excellent sources of help), it's gnereally a good idea not to get yourself banned from a server or channel due to ill advised behaviour.
Away Messages
There is absolutely nothing worse than any type of away message that generates noise. Especially on a busy channel, where such a thing can result in instant banning. Generally, it's in your best interests to turn off all broadcasting "away's" that your IRC client may have. When using a new IRC client, before connecting to a server or going away, you should check to make sure that your away message settings are all set to silent. Especially since a few popular IRC clients come with away message broadcasting enabled by default. Now that I've told you all of this, I'm sure that I shouldn't even have to mention that switching your name based on your various periods of inactivity can also be rather annoying, especially when overused.
Nick Changes
Constantly changing your nick to let us know what you are doing is just as annoying as using an away message. It is not necessary that we know that you are going to the bathroom by changing your nick to John-Doe-Pissin or that you have wondered outside to check the mail by changing your nick to John-Doe-Postalbox. No matter what you do, nick changes you perform show directly into the channel and get very annoying to see constantly. If you are going to be away from the computer, simply use an away message that does not announce when you do /away Gone Pissin to the channels you are in. Pick a nick and stick with it for as long as you shall live. Or if you want to constantly change nicks, do it BEFORE you get into the channel or AFTER you leave the channel. Buffer space is quite precious and doesn't need to be filled with: John-Doe is away Cuz I need to piss or John-Doe is now known as John-Doe-Pissin.
L33t speak
On IRC, it's very important for users to be able to understand what you're saying, so, obviously, sp43k1ng with symbols and numbers in the place of letters is not a very good thing to do if you really want to be taken seriously. Using painfully bad grammar and ridiculous amounts of nothing but smiles generally go along with l33t speak and both practices are frowned on.
Punctuation
It is also very important to understand that using excessive punctuation isn't necessary as well. If you ask a question and use 10 ?'s after it doesn't automatically mean everyone is going to jump up and start answering your question just because you feel it to be so very urgent. The best way to handle things is to type your sentences/questions just as if you would in real life on paper or something similar. Excessive punctuation only draws attention to you as being in a hurry and sometimes it's even considered rude. One exclamation point(!) or one questionmark(?) is plenty of punctuation to get your point across.
Asking Questions Properly
If you go to a channel and need help with something remember to be polite to those that you're asking for help; of course, that is if you want a response. Remember that the people there are not there for the single purpose of helping you, they also have other things to do and thus if you're being rude and nasty, chances are that they will do those other things instead of helping you with your problem. And you could be kicked and/or banned from the channel if rudeness persists. And it's always good to say thank you after being helped by someone (regardless of whether they were succesfull in fixing your problem). It doesn't take a lot of effort and it really is a good thing to do, if only because it makes people more willing to help you in the future if they remember you as being nice.
Common Sense
Alltogether, there is no better way to figure out what is tolerated in a channel and what is *not* tolerated in a channel by asking someone, reading the topic, or reading any rules webpage for that channel.