Scanty dress is considered offensive everywhere, so carry a sulu to wrap around you. Women should cover their legs while sitting down and their thighs at all times. Never stand upright before seated people, and try to enter a house or maneapa shoeless, and from the lagoon side rather than the ocean side.
If you're planning to stop at an outer island, take along things like matches, chewing gum, volleyballs, fishhooks, T-shirts, cloth, and cosmetics to give as gifts. Don't hand them out at random like Santa Claus—give them to people you know as a form of reciprocation. It's the custom.