Regarding Astrology specifically, devotees will point out how easy it is to test scientifically. Setting aside any notions on "how" it might work, simple, observable tests have been published. In very repeatable findings, a gathering of professionals, isolated from one another, but working in the same place and at the same time, can be given the randomly selected birthdate and map coordinates of a person from history. Not only do the Astrologers produce "readings" for this person that are alike in details, the findings match the historical record of what the person was actually like.
Concerning the "how it works," like feng shui, Astrology can be considered a documented set of observations -- one generated and refined over thousands of human generations -- that has produced a canon of referenceable data on predicting outcomes based on recored precedent; that's all. One does not need to think the "planets speaks" to give due to accurate information, when accurate information is provable.