Congrats on the big life decision, wt, you must be very excited (and a little nervous?)
I have a little teaching experience. I tutor math on and off and also teach ESL to a varied group of adults at the public library in my city. Honestly I've found the best results by far come from working one-on-one with students. That's the best way to really get a feel for what problems people are having and how they think. A lot also depends on the goals of your students. One year I taught math to a girl who was being home-schooled. She hated math and her parents just wanted her to pass standardized tests. Since we only met for an hour once a week all I had time to do was walk her through practice problems and check her on the ones I assigned her the previous week (which she usually hadn't finished). She passed the tests but honestly, if I had been teaching her as one person in a group I doubt she would have gotten enough attention for even the limited results we got, there just wasn't enough interest or time. On the other hand the best experience I've had was tutoring my brother. When he was falling behind in high school math my parents started dropping him off on Saturdays and we'd have the entire day (sometimes he'd even sleep over). That way we could work in depth and really figure out his strengths (probability, geometry) and weaknesses (factoring polynomials) and focus on them accordingly. We also had enough time that when his brain started to get tired we could take a break and watch a movie or walk to the diner or something. I think that's the ideal teaching situation but it's understandably very rare to be able to do that.
The people I teach ESL to come from all different backgrounds, and there's a wide variety of proficiency-levels. To be honest, we're not really equipped to deal with people who have almost no English, which is unfortunate since they're the ones who need the most help. I've worked out a couple contingency lesson plans (I've been collecting pictures; I've found some old catalogs at thrift stores that are very useful for working on basic vocabulary) for when people like that show up, but being able to do that all depends on how many students and teachers show up on a given night, and I haven't really worked out a long term plan which would require setting some concrete goals and assessment tools. As for the rest of the class, sometimes we have them work in groups on grammar problems, or practice reading out-loud and then answering questions about it, or more generally work out topical lesson plans designed to give conversational practice. The ones I've found the most popular so far are various sorts of matching exercises where they work in pairs (or teams) and are each given a similar item or set of items with incomplete (but interlocking) information. They have to work on describing them to each other in order to complete their information. One example (that is very easy to prepare) is a crossword puzzle where one person (or team) has the vertical entries filled in and the other has the horizontals. They can't give the words to each other but have to think of a definition, or paraphrase, or come up with an example sentence where they leave the word blank and the other team has to guess. Another example that's even more popular (but harder to prepare), is to give them two sheets of pictures. Some of the pictures are identical, while others are largely the same but have differing details. The goal is to take turns describing the pictures in as much detail as you can, so you can figure out if your pictures are identical or different.
Hope some of this is helpful, and have a really great time in South Korea. I visited for a month (in 2006) and it was beautiful.
How do you get hired teaching young children with no apparent degree or experience in the area?
The high demand for English teachers in some countries. I have a good friend who was a monolingual Computer Science major with no real teaching experience before he got a job teaching English in South Korea (2003-2008). Of course, there's a wide variability in the quality of teachers (and schools for that matter), as you might guess from the fact many of the teachers my friend worked with didn't even bother to learn any Korean.