The reading thing traditionally involves what we call Greek coffee or most people Turkish coffee. After you drink your coffee the fortune teller will turn the cup upside down in a saucer and read the patterns created by the coffee ground. https://en.wikipedia.org/---/Turkish_coffee
This coffee is still quite popular, but younger generation prefers the all time classic Frappé or more recently all local variations of various Italian etc coffees -Greek style, say Freddo Cappuccino, Freddo Espresso and the likehttps://en.wikipedia.org/---/Frapp%C3%A9_coffeehttps://en.wikipedia.org/---/Cappuccino#Iced_cappuccino
I think due to this fact and of course because most people nowadays don't believe in such things, coffee readers are not so common as they used to be.
Personally I don't think one can foresee the future through tea leaves or coffee or whatever, but I think it's statistically possible to make mostly right predictions for the future, especially if you know the people you make predictions for/you are familiar with their circumstances and/or if you have a keen eye for details and so the ability to get hints for people you don't even know.
Often simply how one speaks or behaves or is dressed can reveal a lot about his/her character and circumstances, so often you can guestimate things and be correct...