The etiquette, that forms part of IRC use, is the same as in most areas of life as well as those used on other forms of social media.
Joining an IRC network for the first time presented me with a challenge of a port being misconfigurated on my WISP. Googling the error let me to the South African community/loco of Ubuntu and, using their website, I was able to at least connect to them to find out about my error. And the first thing I did was to ask if I can ask a question (regarding my issue). This got a response in the line of “do not ask to ask man, just ask.” Today I realise that it was quite clear why I was there in the first place – I needed help with something – and their purpose was do provide help. So it is only natural to expect that I would have a question and that I can just go ahead and ask it.
While it is possible to use colours and special bold, underlined and what not text in IRC, this is mostly frowned upon. With most user on IRC being more technically inclined, it is also of no surprise that some would actually use IRC from their terminal windows as oppose to using a GUI. And in the history of the terminals, terminals were not always able handle these special text and would simply crash when they had to deal with them. Another reason for not using them, is that they are complex and might scare away new users. If you need to highlight something specific then use the correct/better words to do so.
Like all forms of electronic communication, typing in ALL CAPS is seen as a form of shouting. It is also regarded as being very rude. We do not shout in public places, nor at home and the same is expected on online communication.
When asking a question, provide as must detail as possible of what you are trying to do. On technology related channels it will be helpful to provide the program name and version. The system you are using and its version. What you expected to happen and what happened instead. Any output or clause that you might have gotten. Also show that you have put in some effort to solve the problem yourself and mention what you have tried so far.
If you have issues with some form of code that you are trying to implement, then do not paste your code in the channel. This practise is regarded as channel flooding and may get you kicked from the channel. Rather use a public paste bin and provide the link to it in the channel. Also try to create the most minimal form of code that has the issue you are experiencing – no one wants to digest more than 30 lines of code just to have an idea of the issue.
Only ask your question once. If you do not get an immediate reply then give it a few hours. It is very common for users on #ubuntu-za to get the response that they might get an answer after about 8PM – when family time for most users end. If no one seems to have noted your question after a few hours, then fell free to ask again. Also do not leave the channel a few minutes after asking. Because when someone becomes available to help, they will not be able to do so since you are no longer there.
IRC is a bit unique in that it is possible to have programmable bot in the channel. This is quite nice to greet new user when they join the channel for the first time. It makes them feel noticed and not feeling left in the dark. This is probably one of the reasons that I stayed on the #ubuntu-za channel in the first place. If possible, having a real human form this role also adds some human touch to it. Pensioners, someone that is on the PC all the time or the use of shifts might help with this.
This is another general case. Be aware of any personal details that you might give on these networks. You do not know the intent of all users in a channel – especially the random ones – and what ever you say in a channel gets broadcasted to all it users. Some channels are also logged to the web, therefore keep from saying things that might get used against you in the future.
It is rude to ask nosy questions, especially if you are new to a channel and it does not relate to the topic at all. Also understand that anyone helping you has a life of their own and they may need to leave while helping you. And when you want to send a private message to someone for the first time, ask them, on the main channel that you are on, first before doing so.
Most channels will allow for general conversation. In some it might even be a good idea to get to know the other users better. But be aware when it will not be allowed in a channel. And unless if you are in a channel dedicated to religion or politics, just avoid these topics. These are regarded as sensitive topics and can easily turn into a conversational war.
When you have to leave your keyboard/computer while being part of a conversation, excuse yourself with things like wbbl (will be back later) or afk (away from keyboard) then mark yourself as away using /away. When you are not part of any conversation then just mark yourself away silently. There is no need to inform the whole channel, unless if you know someone will be looking for you and you want to indicate when you will be back.
Do not make use of scripts that announce your every move, song you are listening to, news you are reading etc. They are just an annoyance in which no one has an interest and they use all the fancy text already talked about.
Everyone on the channel is adults and expect you to act as one too. Do not use foul language, nor language that discriminates against any race, gender or other social group. If you are not in a language specific channel, then speak English to allow all to participate in the conversation. Also use proper grammar (as far as your possibility allows) that clearly communicates your indent and take care of some punctuation as you feel might be needed – ie do not use repeated punctuation (or smiley faces) just for effect.
When you want to speak to someone specifically, and especially if they are marked away or are idling, then mention their name/nick (best as a prepend followed by a double colon) in your message. And again to not leave the channel if you expect them to respond.
When you have been able to learn a lot from a channel, consider staying there to give back to other new users that may join the same channel in time. Overtime it will likely come off as rude if you just ask questions and take from the community without giving anything back over time.