This question was made in a comment regarding my article on Amethyst.
QUESTION: "Where and when should I place the amethyst stone?"
MY ANSWER: My brief answer was: It would differ depending on the need and use of the amethyst. In general, placing it on the affected area or related chakra at any time safely is the way to go.
That is the general idea: Safe and where it is needed, any time. With that principle you can get the crystal energy. Let's get a bit more detailed, though.
The first thing in this, as with any crystal work, is intention and clear energy. Before working, it's best to clear the energy of the stone. Set your intention with statement and prayer that the work is for the highest good of all concerned. I find it best to ask the crystal for its help in the work as well, and you may want to charge the crystal.
Once you have a cleared crystal and sparkling intention for using the stone, choose the time for your work to coordinate with both the needs of the person getting the crystal energy and anyone working with them. .For most applications, a time when all can be in a calming setting when it's quiet is usually ideal, but most environments have potential to work as long as it's safe. For instance, the only time I recommend using crystal energy while driving or the like is when wearing it as jewelry or carrying it in a pocket. Doing it in the living room while watching the children may scatter the energy, though, but as long as it's safe for everyone, it can be done.
There are many direct ways to bring the energy of the crystal in contact with your own energy field. Crystals can be, as I said, worn as jewelry or carried. That is a very basic and easy way to bring their power into your own auric field for healing and blessings they bring. It is one method that can keep an ongoing energetic connection with the stone's vibration as you go through your day. You can also place the crystals on an affected area that it is working with you to heal. In the case of body parts are awkward or uncomfortable to rest crystals on, the crystal can be held a couple of inches away over the area, or placed near the related chakra. Another possibility is crystal elixirs or gem essence, which can be used on virtually any part of the body. Still another is to hold the crystal in the palm of your receptive hand -- left, if you're right handed, right if left handed. Indirect methods such as crystal grids can also be used.
How much and how often you want to use a crystal for healing work depends on the situation. Three to four times a day for concentrated crystal work is often a good choice. Sessions of 10 minutes to an hour work for many. Generally the longer the session, the fewer times a day it would be done unless in extremis. If the person receiving the crystal energy feels uncomfortable or has unpleasant symptoms, take a break. When energy moves very quickly, it can be disconcerting. If this happens, breathing exercises and a short time to relax quietly can help regain balance. Later, once feeling more centered, you can try it again for a shorter period. It often helps to build up from a short session to a longer one. Working with crystals, as with all more subtle vibrations, is best done regularly, daily or every other day. Practice will help you get a sense of what works best for you.