Start by holding the crystal under cool running water for several moments, visualizing a ray of clear light penetrating into the heart of the crystal. This is an easy way to cleanse and clear the crystals. Since crystals can pick up negative energies from what is around them, or when used for healing, this process needs to be repeated at regular intervals or whenever you feel intuitively to do so.
Then charge the crystals by placing them outdoors in sunlight (never do this with citrine or amethyst, as the color will fade quickly) or moonlight, within a crystal grid, on top of a crystal cluster, or near or touching one you deem powerful, for at least 24 hours. Leaving them outside in rain and snowstorms also gives then an extra boost.
Meditating while holding the crystal can be an amazing way to increase feelings of peace, harmony, and acceptance of life situations. It can also be a gateway to other dimensions of time, space, and consciousness, increasing intuition and understanding.
As crystals amplify energy, be aware in this process. Be ready to face past feelings, emotions, and memories that need to be transformed in order to move further along the spiritual path.
Above all, using crystals requires you to be open to what is happening in your life. They will give you the ability to see old patterns and stuck energy that need clearing. Trust in your intuition.