Usually, the point of the story will give you some good clues as to how the person wants to think about the topic. There are various tools for extracting more complete information about these topics which you can try out. Or there may be terms to describe the effects of yaqona, with colorful metaphors. This kind of information may be hard to collect, as your informants will keep thinking this is a test. But is still worth a try.
Some topics work better than others.
We had some good success in PNG with eliciting insults in the local language. It ended up being quite valuable for finding out about how people thought of the body. These can be difficult to make up, but it may well be worth a try. If you want to design some of these related to topics of interest to you, you might try them out among yourselves to see what your colleagues think, or you might try them out on a Fijian friend to see how they work. In this way you can refine them before you actually do your little study with them.