If you want to change your nickname for any reason, (for example I might want to change Silent to SilentBusy or SilentAway if I was going to get some food or something) it can be done very simply, all you need to do is type
/nick newnickname
And thats it. Told you it was simple.

Another common thing that people want to know how to do in IRC is an action. When you just type something and press enter, it would appear like this:

< Silent >I am going to teach you how to do an action now

an action would appear like this:

* Silent is teaching you how to do an action

to get this result, type

/me action

where the 'action' is what you are doing.
It's called an action because it describes to others what you are doing as opposed to actually saying something.

Private Messages are a very important part of IRC. They are used when you want to say something to someone without everyone else in the channel finding out. It may be because you are planning a surprise for someone, or you need to talk to someone about something personal. Whatever the reason, here's how to do it.
Simply double click on the nick of the person with whom you want to chat (the list of nicknames is down the right hand side). This will open up a new window (often called a box). Any message you type in this window will be delivered to your chosen recipient only, and anything they reply to you will appear in this box too.

In IRC a lot of people use abbreviations to avoid typing out common things again and again. A full list of all abbreviations ever used would be huge, so I'm going to just try and cover some of the more common ones: