The Yasawa Islands have a population of several thousand Fijians, spread across a dozen or so villages on the larger islands. Visiting these villages — as opposed to staying in a resort bubble — is one of the most rewarding things you can do in the chain. The welcome is warm, the ceremonies genuine, and the experience far removed from anything on the tourist trail in Viti Levu.
The standard protocol is the sevusevu, a welcome ceremony conducted with the village chief, in which you present a gift of kava root (available at markets in Nadi or Lautoka before you depart) and participate in the communal drinking. Without going through this ceremony, you are technically an uninvited guest; with it, you are welcomed as a temporary member of the community and free to wander the village, join meals, and talk with residents.
Most resorts in the Yasawas organise village visits and can advise on the correct form. Some budget bures are operated directly by village families, which means you are staying in the community rather than visiting it. If you want the most genuine version of this experience, ask your accommodation whether meals are shared with the household or served separately — that distinction tells you a lot about how connected to village life you will actually be.