Travel by air if the island you want to stay at is unreachable by boat. Four main airlines have inter-island service flights: Island Air, Pacific Wings, Mokulele Airlines and Go! Airlines. Sometimes these companies will hold fare wars, which will drop the ticket price. It's possible to get a pass for however many days a person might stay.
Ride a ferry to visit nearby islands. Service is avaliable between Maui and Lanai as well as Maui and Molokai. The two main ferries are "Expeditions" and the "Molokai" ferry.
Take a cruise if you wish to see all seven islands and spend a little time on each. This is a great option for those who are visiting Hawaii for the first time.