I've got one little rule for expat life in Korea. It's a simple one, but I've found it to be fairly effective wherever I've gone:
Don't be a wanker.
Welcome to Korea, I hope you enjoy yourself, but please don't be tempted to act like an idiot just because you're in a new and exciting place. Like it or not, you're a cultural ambassador for your community and when in Korea, you need to respect not only the local laws, but also the people around you. I'm not saying you shouldn't have fun, but be aware of the consequences of your actions. Last year Ask A Korean wrote a great post titled "Ask a Korean! Wiki: How Not to be an Arrogant American?". It's worth a read and it applies not just to Americans, but to every foreign visitor or resident in Korea.