Readers of crystal balls say that gazing into the centre can aid the ability to look beyond the physical world into the spiritual realm, to communicate with loved ones who've passed on, gain insight from spirit guides and see messages about the future.
North American shamans referred to quartz crystals as light-stones and believed they were "splinters from the Heavenly Throne." As such, they became a crucial element in their bid for clairvoyance. Druids also used crystals for scrying and traditional Scottish Highlanders called them "stones of power." As well as divination, crystal balls have also been used for healing. The Ancient Egyptians used crystal spheres as a means of concentrating the rays of the sun onto a particular area of the body that needed healing.
When choosing a crystal ball, use your intuition and be guided to one that feels right for you. Some people prefer totally clear and flawless items, whereas others feel guided to choose ones with small flecks or imperfections. The thing to remember is that it doesn't matter what it looks like to other people, it's how you feel about it and can relate to it that matters. If it feels right to you, than go for it! Take time to become familiar with your crystal ball before you launch into using it - a good way is by meditating whilst holding it and trying to connect with its energy.