Crystal balls are an ancient form of divination. Scrying with a crystal sphere – spheromancy – is a specific form of divination known as crystallomancy (also known as catoptromancy). Crystallomancy in general refers to scrying using any reflective surface, such as a pool of water in the moonlight or a polished mirror.
The crystal ball itself is obviously of vital importance and should be chosen carefully. Use your instincts when buying – it’s easy to say that one glass sphere is the same as any other, but you may find one that “calls out” to you. Whether this is due to the crystal ball itself or to other factors such as the seller or your mood at the time is irrelevant. Try to buy a ball that gives you a positive feeling.
Once you have a crystal ball that is effective for you then you should not let anyone else use it. That’s not to say that other people can’t be present when you are performing a reading, nor to say they can’t look into the ball. However it is your crystal. You should be the only one to gaze into it for divinatory purposes. The more you use it, the more attuned it should become to you – and you to it. Allowing anyone else to scry using your crystal – or worse, allowing someone to use it “just for fun” – could dilute this psychic rapport.
Ideally no-one else should ever touch your crystal ball.
Similarly you should keep your crystal carefully wrapped and stored when not in use. Do not leave it “on display”. It’s not an ornament, it’s a divination tool. Having it where you see it a hundred times a day will devalue its importance.
Treat your crystal ball as special and hopefully it will give you special visions when you ask it questions.