A few things to be aware of when you are travelling in South Korea:
Greetings. To greet someone in Korea, bow slightly and say the polite and general greeting, “Annyeong-haseyo”. Waving isn’t suitable for elders.
Yes and no. The gesture for “yes” is a simple node, but “yes” in Korean language it sounds similar to “no” in English. The gesture for “no” is a light headshake. But generally answering by only gesture without words considered rude, especially to elders or strangers. If you want to say “yes” in Korean, its “nae”, “no” is “aniyo”.
Table manners. Table manner is one of the most important etiquette in Korean culture. A spoon and a pair of metal chopsticks are the basic cutlery. Don’t hold the spoon and chopsticks at the same time, or use both hands. Use a spoon for rice and soup, and chopsticks for side dishes. In restaurants, side dishes and rice are free for refill. Yawning near the table, making a lot of noise with your cutlery, chewing with mouth open are rude behavior. If you are eating with traditional Korean family, it’s custom to wait until the eldest (or head of the family) eat the first spoonful.
Both hands. When you hand or receiving money, a glass of soju, or anything from strangers or elders, it’s a sign of respect to put one hand below the other hand.
Tipping. Tipping is not customary in Korea. It might be even considered as a rude gesture.
Shoe politics. Keep your outdoor shoes outside. Inside a house or office, you may be requested to wear indoor sandals or slippers. And inside a bathroom, there may be an even further pair of footwear to change into!
Sacred places. Temples are open to general public but remember not to make loud noise, and remove your shoes and hats when entering praying rooms.
Gestures. Pointing someone with the index finger is considered rude in Korea. Instead, indicate using your whole hand, especially when gesturing towards someone.
Physical intimacy. It’s custom not to show physical intimacy in public places, especially between couples. Hugging is not a common way of greeting.
Privacy. The concept of privacy is a little different in Korea than in western countries. Although it’s not so severe anymore, people may stare at you for looking different.
English language. English is widely understood in the cities of Korea, usually between young people. They understand a lot better than how much they speak. Lots of signs and names are written in English in big cities.