The best advice i can give you is to practice practice. You should also learn to work with your energy more. Using energy is also good for divination. Meditation is the key to working with energy. Becuase while meditation lets you see things in your meditative state. It also helps you relax and calm your mind. Crytal balls are used for gazing and scrying too. Most people meditate before they do divination, some go into trances to help them see images. And most people can just stare into the crystal ball and start seeing images. But which ever will work for you.
Scrying is another form of divination seeing an image and interpretating that image on what it means. Some scrying can be used to see the future, but remember the future can always change or is always changing. Also when working with tarot, or scrying i would keep a journal to write things down on what you see or feel it really helps a lot when practicing.
I hope this helps you out some.
Dark Blessings ~