Type /list to display the channel #s and channels associated with them. It will display something like the following if you are in at least 1 channel:
Channels: 1=General(198)
Find the # next to General, in the example above it's 1.
Use /# to speak in that channel.
Such as:
/1 Hi all in general chat.
NOTES: If you join general it auto-spawns another general# channel, most of the time, you won't be able to speak in the general. It will show up on your computer, but no one else will see it, and you'll be able to see some if not all of the others in the normal General channel (not an auto-spawned version with a number at the end).
If you want to join a serverwide channel, it's in the form /join serverwide.
channelname[:
password] or another channel on another server takes the form:
server.channelname[:password] Hope this explains it well enough for you.
Yther Ore.