Joining the IRC is preferred but most people don't know how to use it.
With your favorite IRC client (HexChat is good, you can also use Rizon's web chat), join #disc0rd on irc.rizon.net.
That's all that's required.
The IRC channel is bridged to the #general channel in the Discord, so you'll still be able to interact with the same people.
Your messages will show up with the default bridge avatar unless you change your bridged avatar. To do this, type
:avatar <URL to avatar image> and that image will be your avatar on Discord.
If you want to join an unbridged channel, join #disc0rd-irc instead. That channel is not connected to Discord at all.