I would say the top few categories of questions are IRC registration, applications (almost always specifically the code), and, strangely enough, "is 001 really going to kill me?"
I'm not sure how to address that last one but registration needs to be laid out very clearly. You mentioned some simplified commands in chat that are set server-side - those would be a good start.
Other than that, we should list our rules and how to register/connect with the widget on the guide page BEFORE anything about other clients.
At the moment instructions on the connecting tab start with registration, before going onto talking about clients, moving onto discussing instructions specifically for mibbit and chatzilla - both with a step about going back up to registration. This is suboptimal.
I suggest we move everything about other clients into another tab or section and have a section about "connecting using the chat client on this page" that goes something like this:
Choose an appropriate name, hit enter
Register using the following commands (You only have to do this once, unless you don't use your name for over 30 days):
[registration commands]
Now, "identify" using the following command (This is the irc version of logging in, you will have to do this step every time!):
[identify commands]
Now, you should be able to join the chat by doing /join #site19