Korea Visa Waiver, visa free entry ranges from 30 days to up to 6 months for Canadians. It depends on your nationality. Teachers often get an E-2 Visa, or professors an E-1. Korea also has a working holiday agreement with a number of countries.
"The Foreign Language teaching (E-2) visa is issued to foreign language teachers who work in South Korea. Applications are required to be native residents of a country whose mother tongue is the same as the language they will teach and they are also required to hold a bachelor's degree from that country. Applications are required to submit criminal background checks, health checks, sealed transcripts, verified copies of their degree, contracts and a fee to obtain the visa."
South Korea Tourism Video
North Americans entering Korea
Most North Americans arrange a teaching position through an agent, and get their working visa before they leave for South Korea. Be sure to ask around at the forums on teaching English in Korea, to find a good recruiter and recruitment agency. Some of them can be a nightmare!
Peter Burnside on going to teach English in Korea:
"Follow your heart, trust your instincts, and take insane risks."
p. 443, Teaching English Abroad, Susan Griffith
Year One in Korea
Many teachers sign a contract knowing it won`t be the best. But they complete the first contract and look for their second more lucrative job while doing so. They sign on with the first school that hires them, then ask around and try to get a better job in year two.
You could wait to go to Korea to land a job, but it is more difficult to obtain a visa. Moreover, officially you are not allowed to work if you come on a stay permit, however many people do. Few schools will ask for a work permit according to Geoff Crowther and Choe Hyung Pun of the Lonely Planet guide on Korea.
"The B-2 status allows travellers who are passport holders of various jurisdictions, including the People's Republic of China mainland, to stay in South Korea for a maximum period of 30 days, provided that they are using Incheon International Airport as a transit stopover. It applies to ordinary PRC passport bearers when they are travelling between the Chinese mainland and Canada, the United States, Australia, New Zealand, Japan or 30 European countries. The B-2 status is encoded in Article 7 of the South Korean immigration law."