There's no magic or trick. They simply come up with 9 different types that are very standard and the rest is done by our minds. I could make up one type and tell you why it fits you. You would immediately feel that I am right. Months later after you forgot what I said, I could say to you something else and you would still think I was right.
That's how psychics work. They find some common ground and come up with a phrase that fits anyone, but you hear it and believe it's true. Well, it's true for everyone... nothing unique.