DON'T sit until told where to sit.
DO note that the eldest are served first, and they also begin eating first.
DON'T use your chopsticks to point at something and never pierce food with your chopsticks.
DON'T cross your chopsticks when putting them on the chopstick rest.
DON'T eat with your hands.
DO try a little bit of everything. If you don't know what something is, ask!
DO refuse the first offer of second helpings, out of politeness.
DO eat everything served to you.
DON'T ever place your chopsticks parallel across the bowl. You can indicate that you're done eating by putting the chopsticks on the chopstick rest or simply on the table.
DON'T criticize Korean cuisine. South Koreans are very proud of their food and will be insulted if it's criticized.