How does an astrologer make their predictions?

A person who studies the movements of the sun, moon, and stars in order to predict future events.

“A LOT of people want to know the usual nonsense things​—when am I going to make a million dollars or when will I meet Mr. Wonderful?” says a part-time astrologer. ... Thus, knowing a person’s time and place of birth, an astrologer can construct a chart, or horoscope, showing the positions of the stars and the planets and interpret the factors that may influence that person’s actions at a particular time.

Like chess players, men predict solely on the basis of what they see before them.

However, the Bible tells a different story. “No prophecy of Scripture springs from any private interpretation. For prophecy was at no time brought by man’s will, but men spoke from God as they were borne along by holy spirit.” (2 Pet. 1:20, 21
The Lord's Pray, (Matthew 6:9,10) is a prophecy about a Government that is to come, here on earth. Matthew 24:7-14, also 2Timothy 3:1-5 tells some of the things to look for.
Astrology was not used for this information about the future, you can read it for yourself, from the Bible.
Ref: jw.org (Astrology)