We're working on 6 years of full time Pacific Islands cruising and
you're right; in some places it's harder than others to meet the
locals. In any place with a population of less than 50 and somewhat
off the beaten track (there are dozens of these) you will be a major
attraction. Expect to be invited to meals and celebrations of all
kinds. The cost is that you will be expected to give a speach or sing
a song or dance a dance or in some other way provide some entertainment
for the local folk... Pictures and movies can be good too. Prepare
something in advance. In bigger places you may find that some cultures
are more interested in guests than others. In the Pacific making
genuine friends with a Tongan takes a major effort but in parts of
Vanuatu and Fiji if you show up in the same bay twice in a decade
you'll find yourself adopted into the local village...

If you are interested in local cultures it really helps to stay for
some time in the places that interest you and take the time to get off
your boat and talk to the locals! Visiting the local church or shool
can be a good way to meet folks, but making an investment of some time
is the best bet for really getting a feel for the local situation. For
example, we spent two months in Niuatoputapu this year. We were one of
the first boats of the season to arrive and one of the last to leave.
While we were there more than 70 boats came through. Most stayed for
less than 3 days, many never got off their boats and, of course, most
didn't meet any locals who weren't selling them something. By the time
we had left we had met most of the locals, had dozens of meals with
them and knew a good deal about them. By contrast, and despite the
fact that there were weekly pot lucks, where we went and took notes, we
knew hardly any of the cruisers who passed through...

-- Tom