Lao Ocean Girl provides some great tips and questions to think about while doing the telephone interview. I’ve posted a few that I thought struck a cord with me. I suggest you check out her site as she posts good information on teaching on Korea as well.
How long have they been in Korea? (Are they all newbies like you? That could mean the school is not that good, and they have a high turn around rate. Are there teachers that have been there for a 2nd or 3rd contract? If so, that tells you volumes about the school.)
Will you be working a split shift? (VERY IMPORTANT. Sure, you’re only working 30 hours a week, but a morning and afternoon split shift just wastes your whole day and tires you out. I would NOT recommend teaching kindergarten students. [My first year teaching kindergarten was torture!])
You can find rest of her post here.