Yes, I know we all know this. But a proper bow is an indication of your level of respect. So, don't just nod your head. Koreans are an odd bunch. Like in most Asian cultures, our mannerisms are very courteous to the extent that they even seem aloof.
Physical contact is a no no.
Don't be surprised if you see men in Korea with their arms around each other's shoulders. Young boys even hold hands. The same goes for women. But PDA between members of the opposite sex are a serious breach of Korean etiquette. That's because it's impolite to talk too much during the meal.