Ganghwa is separated from the Korean mainland by a narrow channel, spanned by two bridges passable by cars. North Korea is directly across the channel on the north coast of the island.
Ganghwa is the site of a number of significant architectural and archaeological locations, but it is not on the beaten path for western tourists. It is also a place of heightened military presence and western tourists would be wise to carry their passports with them as a precaution. Nonetheless, the people of Ganghwa are extraordinarily welcoming, though it is obvious that they are not accustomed to seeing non-Koreans in the neighborhood.
There are frequent direct buses (W4200; 90 min) from Seoul's Sinchon Bus Terminal to the main town of Ganghwa-eup, as well as Bupyeong Station, Hapjeong Station, Songjeong Station, and Incheon Bus Terminal in Incheon. Local buses also connect to Gimpo (the city, not the airport).
Bus 3000 and 32000 from Seoul also take about 90 minutes and end at the Ganghwa bus terminal. Ganghwa has island busses that travel the perimeter of the island and most major tourist stops. There is also a "tourist bus" (bus one going counterclockwise and bus two going clockwise around the island) in theory, but they are harder to catch than the public bus. Your Seoul T-money card will work on the Ganghwa busses as well.
There is a tourist information located inside the bus terminal. No English is spoken but they have English language tourist maps. There is also a tourist information center at the ferry terminal in Oepo-ri. They speak English.
Local buses appear to be infrequent.
Ganghwa Ginseng and Hwamunseok, which is a mat woven with flower patterns a representative traditional Korean product, with its intricate handwork and designs.
For a quick, western friendly meal, there is a Paris Baguette on the island, and the employees speak some rudimentary English. It is right next to Ganghwa Middle School and near the bus route.
There are several motels and yeogwan in Oepo-ri.