Occasional buses
connect most points on the island. They run several times a day in the central plain, but are far less common outside with twice a day buses only on weekends for the Northern coastline, for instance. The bus center is in Sawata, close to the unmissable golf practice range. You can buy 2-day tickets for the whole weekend for ¥2000. Detailed timetables are available at the Niigata Kotsu website (http://www1.sphere.ne.jp/...) in Japanese.Hitchhiking
is a fairly good means of getting around.You might want to consider renting a car some rent a car in Ryotsu after getting off the ferry. Although the island is not very large, keep in mind that the coastal scenic roads are quite windy. A round-the-island drive following the coastal road would be over 250 km long, and take at least a day.
Bicycle
is an option, but accessing the more remote outer coasts, where some major tourist spots are located, will require you to climb some strenuous passages.