How to select which supernatural to believe?

[Belacqua]

certainly anything that claims to predict the future etc... such as astrology

Agreed -- this is frustrating. It's not only unbelievable, it's even a dumbing-down of what people used to believe about the supernatural and astrology. 

Back when respectable people believed in these things, astrology was not considered supernatural at all. It was just a part of nature, and the influence of the stars and planets was thought to be part of the way the world worked. The exact method of influence wasn't clear, but then there are a lot of natural things that aren't precisely explained, even today. The powers and energies of the world were woven together and people didn't assume that planetary influence was other than part of nature. 

When explanations changed, and planetary influence was no longer believable, apparently people moved astrology into a sort of catch-all category called "supernatural," with no clear definition.

Nor was astrology generally used to predict the future. It could suggest trends and days that were more or less under the sway of the desired influences, but it wasn't as if your future was decided by the stars. It was more like the weather, or like personality tendencies which you could take account of in making plans.

Partly the modern dumbing-down comes about through a change in what the word "supernatural" means. In the old days it had a precise meaning -- unlike the modern term which seems to mean just anything that isn't science. 

People assumed that every kind of thing has a nature -- a set of characteristics or qualities, and a set of potentialities and limitations. It is the nature of a cat, for example, to eat, play, and nap, and not in the nature of a cat to fly to the moon or compose opera. If a cat did something which was over and above (super-) its nature, then that was supernatural. A person who could do more than it is the nature of people to do would be considered to have supernatural powers. So the type of thing which was called supernatural was narrowly defined, and did not include ghosts, tarot cards, etc. 

Some of the things we today call supernatural were considered to be occult -- which just means that how they function is hidden. They may well be natural, but how their nature works is not known and is perhaps unknowable. Others were considered to be natural -- again, astrology was thought to be an aspect of how nature operated.