At my uni, it seems like one or two people bite the dust each contract renewal time, for various reasons. However, all these reasons can be boiled down to "professionalism," or lack thereof. Anyway, here are my top tips for being a professonal and keeping your job at a uni in Korea.
1. Look the part. I have coworkers who wear jeans or cargo-shorts, a t-shirt, and a baseball cap to class. In a land where appearance is everything, this is the fastest way to not be respected by your students, or your bosses.
2. Lay low. Don't stir up trouble and just spend your time flying under the radar. Try to have no negative contact with your bosses. The fastest way to get fired at my uni is to start accusing the other foreigners of things, so that the Koreans have to deal with stuff they'd rather not get involved with.
3. The other fastest way to get fired at my uni is to cancel classes. Yes, people do check!
4. Plan for your classes and make them interesting, helpful and fun. Student evaluations really do matter.
5. Watch what you do online on sites like Facebook with regard to saying bad things about your students, uni or coworkers. Yes, people really do check.
6. Have appropriate boundaries with your students. You are their teacher, not their friend. Never have physical contact and even avoid being alone in your private office with a student.