Summarize:

There are many crystal sellers. People often sell crystals in hippie stores, new age stores, alternative medicine stores, science/educational curiosity stores, at fairs and farmers' markets, as well as at concerts and online. There are even fairs dedicated entirely to crystals. Make sure you find a reputable seller. You will want to make sure the details regarding your crystals are accurate. Look up different kinds of crystals. Visual properties as well as any symbolism associated with different kinds of crystal will impact what they do to you. By spending some time looking at different kinds of crystals, you can find your favorite. You can also take time to learn about crystals for different uses. Quartz stones are the most common healing crystal. They come in many varieties (amethyst, citrine, rose quartz, etc.) and hues. People like quartz because it has interesting properties, it is visually stunning, coming in many colors, shapes and levels of clarity. Other common gems used include: Lapis might help bring calm. Jasper might help balance your aura and promote a sense of peace. Turquoise may help to clear your mind. Malachite might help protect against electromagnetic pollution. Gemstones used for healing can be cubic, trigonal, monoclinic, etc. referring to the shape of its crystal system. There are seven types of these. Gemstones are also valued for their "water" or level of refractive clarity. A great way to find a crystal is to "feel it out." This means choosing a crystal based on how you feel about it. You cannot choose a crystal this way if you plan to purchase online. You will have to go to a store to be near or ever touch the stones. Keep in mind that some crystal sellers may not let you touch the merchandise because crystals, especially large ones, can be fragile and very expensive. Make sure that you ask before you touch.
Find a seller. Pick a type. Feel it out.