So, the first thing I did was sign up to an agency; you can (and many do) look for a job yourself via the internet, but at the same time this can lead to trouble and you ending up in a bottom-of-the-barrel hagwon in the sticks where they consider payment to be an optional extra. Agencies, by and large, screen the schools for you. While you're waiting on them, its best to get all the visa documents you need in order; it took about 6 weeks for me to get everything together, and once I got the contract I sent stuff off to Korea within the week. It sped things up no end.
Right now, I'm trying to get my head around the Korean alphabet and some basic phrases; the schools say that the less Korean you know before you arrive, the better. But not knowing any is just plain dumb. It's all well and good making your kids think in English by maintaining a language barrier, but once you're out of the classroom, the barrier is a hindrance again. I don't know about you, but I want to be able to do most of my food shopping without the need of a translator or resorting to Pictionary. Needless to say, it's tough going; I haven't mastered any phrases as of yet But there is still time.
I'll probably update this more once I get to Korea (this is, after all, more about introductions and the planning) but I hope you keep checking back in on this every so often.