There are different kinds of mealy bug. But they’re basically white fluffy things that love a humid environment. Hosing your plant leaves with a sharp hose (particularly those that don’t get rainfall) periodically can help prevent them.

Treat with neem or eco-oil. For indoor plants you can also try treating with a cotton tip dipped in metho.

There is a new kind of mealy bug in Darwin and South East Queensland- papaya mealy bug - that loves frangipani, papaya and hibiscus in particular. It is very hard to treat and I have not had success with oil based treatments. Treat early, and consider bagging and binning infected foliage or plants.