Adapters
Clothes & Shoes
There are many things that you can buy in South Korea so I would not recommend bringing that many things. Below are things that I recommend you bring and don't bring.
What Should I Bring?
The typical sizes in South Korea for clothes are a small or medium in the U.S. If you wear bigger sizes, I would recommend that you bring enough clothes for the different seasons.
You are able to buy western clothing sizes in stores like GAP, Forever 21, Zara, Mango, Pataya, etc.
Most women shoe sizes run US size 8 and under. If you are a bigger size, I would recommend that you bring more shoes since it will be harder to find your size.
If you are teaching in a school, you will need to wear slippers inside the school. So if you have a bigger shoe size, I would recommend that you bring a pair. The Adidas type of slippers are fine.
The plugs in South Korea have the two round prongs (Euro plug). If you country doesn't use that, then you will need an adapter. I would recommend that you buy an universal power strip like this:
Do bring:
deodorant (it is more expensive here)
tampons (harder to find and more expensive)
condoms (sizes/comfort/trust of the Korean brands?)
candles (if you really love candles, that is. They are more expensive here)
Don't bring:
spices (they have most of the common spices here, especially in the foreign markets)
shampoo/conditioner/body wash
textbooks/books (If you're teaching English, a lot of the schools have a set curriculum)
You can easily buy western sized towels in South Korea so I wouldn't recommend wasting your luggage space with them. Bring one towel and if you need more, you can buy it. Fitted sheets was difficult to find, so I would recommend bringing twin or full sized one. For convenience, I would bring a fitted bed sheet and a pillow case.
Miscellaneous
Towels & Linens
