For grounding one uses brown, black or green stones. The stones/ stone is placed below the feet and usually a clear quartz/ amethyst above the head (crown position) (see also Chakra Page)

Carnelian: A translucent orange-red stone. Carnelian is strongly attuned to the earth. This stone makes you feel comfortable within your surroundings - like having an anchor into the physical world. Carnelian is useful for people who meditate since it clears extraneous thoughts (thoughts not pertaining to the subject) It facilitates direction and control of your life.
Green Fluorite: A transparent, often cubic crystal, green fluorite grounds excessive energy. It prevents over-stimulation on the psychic level, anchoring the intuition into everyday reality while enhancing spiritual perception. Holding a green fluorite wand calms the grounds energy during meditation.
Hematite: Hematite has a metallic lustre. Silver when tumbled, in its natural state it ranges between steel grey, greyish-black, and reddish, and may have red spots on the surface. It is an iron oxide, magnetic, and strongly connected to the earth. It aids people who haven't got their feet on the ground. It sorts out issues, making it possible to move ahead. Hematite dissolves negative energies, transforming them into positive ones.
Boji Stone: A metallic stone with a high pyrite content and a strong affinity with the earth, there are two sexes of Boji stone. The female is smooth and rounded, the male has square protuberances. Aligning chakra's and subtle bodies. Boji stones gently ground after meditation or healing.

Grounding through Meditation
With each intake of breathe, visualize the Divine white healing light entering you swirling within you and being absorbed while the murky, negative and unneeded energy is pushed into the lungs and exhaled out. Place your hands towards the floor, push the ill energy out of your hands, into the floor, visualizing and guiding it all the way down through the framework of the building into the Earth. Do this until you feel you've released the tension, stress and worries from your body.

Once you are ready, begin to see the white light growing within you like a ball. Starting from a small glow until it envelops your whole body and pushes into your aura. Visualize this white light forming a bubble around you, shielding you from negative energy, and strengthening you.

Keep this white light protection with you as you do your working, the white light is pure, positive and healthy. It will shield you from the negative and ill energies you may work with when dealing with an ill patient. It allows you to use this healing light to aid you in your healings.

Give a small thanks and blessing to your Higher Good for taking the ill energy from you and transforming it, and for allowing you to use your healing energy to help yourself and others.

You can do this any time, not just when you're doing workings. It's a great way to realign yourself and calm yourself throughout the day. I use it in stressful situations and when I am making decisions, to being clarity to me.