Crystals have been used through the ages for healing, balancing and meditation. Their perfect atomic structure gives out a constant resonance or vibration that it's believed can help re-attune the body in times of mental or physical upset. Crystals absorb and discharge energy and they work with the human energy field, focusing and balancing the body. It's said that different crystals work with different problems, but the most important thing is to choose one that you're drawn to, either the colour or shape or feel, because that will be the one that's right for you right now. Crystals tend to choose you, rather than the other way round!
Because crystals absorb and discharge energy it's believed they should be cleared every so often. There are lots of ways to do this including burying them in the ground, washing them in sea water, passing them through incense smoke and many more. The way I do it is to simply run them under the cold tap for a few minutes and allow the negative energies to wash away. (Of course, a natural stream is even better!) Let them dry outside in natural light. Some people prefer moonlight, but the important thing is to do what feels right for you.
Now sit quietly holding your crystal and putting your positive thoughts into it. Ask it to work with you to aid healing, either for yourself or someone else, or to focus your mind on solving a problem - whatever you need. Remember, crystals don't have magic powers but they can help you focus your mind, and it's our minds that do everything. Crystals are just a tool to help us, but don't underestimate that help!