This may seem cliche, but the first thing you should plan to bring is an open mind, and a good attitude. This will ensure that your Korean experience is that best that it can be.
Money
Since when you arrive you will be at least two weeks away from your first paycheck you should bring around $500 US (C$750) to cover your first month's expenses.
Clothing
Men who are shorter than 6 feet (183 cm) and who weigh about 154 lbs (70 kg) or less will find everything they need here and so should only pack the necessities. If you are above these numbers, you should plan on bringing what you'll need for a year. Korean people are generally smaller than westerners, and this is particularly true for females. There is a definitely lack of clothing for women of even slightly bigger-than-average proportions. For your comfort, bringing enough underwear is particularly important.
Footwear in Korea is generally not as well constructed, and in bigger sizes harder to find. No matter you foot size I would recommend bringing an extra pair of shoes.
In your work place, you generally won't be allowed to wear sneakers, sandals, jeans, shorts or tank-tops. Keep this in mind when packing your bags.
Personal Products
Koreans generally don't use deodorant, so it is very hard to find. Bring a year's supply! (I hear that the Body Shop stocks deodorant, but it is likely expensive.)
Females that use tampons and are particular about a certain brand, may wish to bring a year's supply. Tampons are available at pharmacies, but the brands are limited and the quality is often low.
Shaving products are available, but in only a limited variety. Your electric shaver should work in Korea. (Many models have an automatic switch to go from different types of electricity.)
Sheets
Koreans generally don't use Western-style sheets. If you require them for your comfort, you'll have to bring your own.
Spices
If you are gourmet, and plan to make western delights while in Korea you need to bring along some of the spices you are accustomed to. Allspice, caraway seed, basil, garlic salt, nutmeg, celery seed, cloves, cumin, onion salt and oregano are difficult to find in Korea.
Vitamins and Medicine
I personally recommend you bring a supply of Vitamin C. You will be entering a foreign country with foreign germs and virus. Ensuring good nutrition will go a long way in keeping you healthy. (I also highly recommend Tums or some type of antacid. If you forget or run out of Tums and you have an upset stomach, I recommend a candy called Polo, which is incredibly effective.)
Of course, you should bring any prescription medicine that you need. You may wish to see if it is available in Korea first, as it might be cheaper. Also, some medicine is restricted, so you should check with your local Korean consulate.
Photos
People will be interested in where you lived and your family. Photos are also good for when you
are feeling a little homesick.
