astrology is nothing but a combination of tricks. My uncle is one in India and he gave me some tips cause I had a frank chat with him. He uses a variety of things to determine a person's "feelings" and then use those to agree with him.
e.g.
First of all the moment a person enters, he "face reads them" to see how sad/happy they are and also apparently face reading can tell you alot about a person's nature.
Second, eventhough he's a kundli astrologer he uses looks at the person's palm and from what I noticed he uses slight mind tricks in that. he would look at a person's palm and point to a line and make a gesture which says something like "arghh if only this line was longer this guy would have everything". That person think "this guy must know his stuff".
Third, he does the kundli by the DOB of the person. Now this is the real master class. There are mainly three places any of which could be "wrong" to get the person in the situation he is. 1) Graha 2) Dosha 3) Ancestors
Now any person in the world can be suckered into this. Even the Queen of England. The thing is first of all 90% of the people won't have their Grahas all perfect. Out of the rest 90% will have a Dosha of some kind. Finally, even if a person escapes both of these you can always use the ancestor trick and tell the person his ancestors are not happy.
Frankly, any astrologer worth his salt is a genius. Not because they are doing something good or anything. The genius is in their ability to make "the sheep" believe in this rubbish.