What should you always do when you come to a strange place?
Herman Toothrot will show up in various locations.
It's well worth your time to talk to him.
There are also many memos and notes all over the island.
Here is what you are supposed to understand after exploring and reading: LeChuck is keeping Elaine in the Monkey Head. Herman has the cannibals' monkey head key, but he won't give it back because they won't return his banana picker.