They usually use a tool called the "Low Orbital Ion Cannon" which is really just a DDoS app with a silly GUI slapped on top of it.
http://encyclopediadramatica.com/Denial_of_Service
also, there are irc servers that people set up for different events, but that's getting more into the chanology side of it.
4chan is full of a bunch of 12 year old script kiddies. They don't even know what a buffer overflow is and they think HTML is a programming language.
They certainly are script kiddies, but they're not as ignorant as you portray them either.
A handful of people using a quality tool like Rsnake's "slowloris" (http://ha.ckers.org/slowloris/) could do much more damage.
Anyone remember smurf attacks? (http://en.wikipedia.org/wiki/Smurf_attack) now that was epic. LOIC is lame.