Oftentimes, my appa (dad) is caught slurping some soup loudly at the table, which bugs my umma (mom) to no end. She’ll start in him, to which he’ll reply that it’s considered polite in some cultures to make noises appreciating the food. (Traditionally, it’s rude to make loud eating noises in Korean culture).
Yes, slurping is rude, but in the wild and woolly world of Korean table manners, picking your teeth with a toothpick is not (just cover the action with your other hand). But don't even think of blowing that nose at the table.
Now, to move beyond personal hygiene... Korean meals are not structured into a multi-course format – there’s really no such thing as an appetizer in Korean food. You may see “appetizers” on the menu at your favorite Korean restaurant, but that’s really more of a concession to the American way of eating. Usually everything just comes out at once, and oftentimes, there’s no such thing as a dessert, either, although some concessions have been made in that area (i.e. slices of orange or fruit of some kind). There are, however, clearly sweet dishes, it's just that their rightful function is not after a large meal has been eaten.
A typical Korean meal has a main dish of some sort, accompanied by individual servings of rice, soup and at least a few banchan (side dishes). A more pared down meal could involve just rice, soup and banchan, or even just rice and banchan. In terms of utensils, for an everyday meal you’ll have a pair of chopsticks (Koreans are famous for using metal ones) as well as a peculiarly long soup spoon.
So you’re sitting there, all of the food has been laid out, now what?
If you’re having a dinner party or there are several guests, generally the eldest/person of honor should be served their food first, and similarly should commence eating first. So try not to start chowing down until they start (same goes for leaving – stay at the table until they leave).
Korean eating is a communal experience. One of the things that is a bit awkward with Korean meals is that when there is a large selection, it’s hard to reach everything. But unlike American-style eating, each dish isn't usually passed around to each person. You should just feel free to help yourself or ask someone to pass something to you if you prefer, or have them "pass" something to you (in their chopsticks!) To partake of a shared jjigae (stew), just use your spoon. I should note that some restaurants are catering to more individualized, Western ways of eating by also giving smaller bowls and a scooper for a shared jjigae.
A note about utensils -- whatever you do, don’t leave utensils sticking up in food – that echoes the method that food is presented ancestral ceremonies. Also, technically you are supposed to use a spoon for eating soup and rice, not chopsticks, which are for banchan. I don't follow this last one so much. I also don't follow the one where you're supposed to not mix your soup and rice. I do that all the time.
Now, on to your personal soup and rice servings -- Koreans also don’t typically pick up their bowls of soup or rice while eating, unlike some Asian cultures. Although, never say never: I can think of situations where it is appropriate – for instance, when you’re drinking the cool broth of a large bowl of Mul Naengmyeon, or when you’re finishing up the burnt rice at the bottom of your dish (Nurungji (scorched rice)) with a bit of hot water, to make tea. But part of the reason is it's also unnecessary; Koreans eat short-grain sticky (glutinous) rice, which can successfully be brought to one's mouth from the table, using a spoon or chopsticks.
Traditionally, it was considered rude to blab away during a meal, but that’s not really the case anymore. Still, the don’t chew with your mouth rule holds true.
When you’re finished, you can leave your utensils outside of your eating bowls/plates. Also, if you're a guest of someone, it's also customary to say "I ate well" or "it was delicious" -- jal muk-gut-sum-ni-da 잘먹었습니다 or ma-shi-suht-suh-yo 맛있었어요.
Readers, let me know if you follow these rules, and if you have any that I left out.