freenode (irc) logging in (just the simple stuff)

Connect to a server:

/connect irc.freenode.net 8001

Creating a user on irc for the first time:

/set nick <username> 
/set real_name <Real Name>

/msg nickserv REGISTER <password> <email>

You're now logged in to irc and own this username (nick). You can use it when you log in later.

Logging in with an existing account:

/nick <username>
/msg NickServ identify <password>

Join a room

/join #<room-name>

Say stuff

This is a something (you can just type in whatever to send a message to the room).

Mention a person (you should usually do this if you want somebody's attention)

<users_name_that_you_want_to_reference>:  Hi there, I'm trying to talk to you.

You can usually auto-complete user's names with <TAB>.

Leave a room

/leave #<room-name>