Cleansing a gemstone or crystal is key right after purchase. It may have many things attached to it on its way to be yours. A cleansed crystal will feel bright and positive. If it feels hot and heavy, it probably needs to be cleared.
Sea salt is the second best way to clean your crystals. It will dispel any disease and negativity. It is also used as a psychic and physical disinfectant. It can be mixed with water or used dry. Place the stones in the container and let them soak overnight. If you are lucky enough to live by the ocean, you can bring the salt water in a jar and soak your crystals in it overnight.
The light of the moon is also a powerful charging agent for stones. Place the stones outside during a full to new moon. Place necklaces in tree branches where the moon will be sure to hit them. The waning moon is a good time to dispel any negative energies from the stone.
Don't place them in sunlight ever. The sun can fade the intricate color from the stones. It can also cause cracking or internal damage if they are left out too long in the sun.
Burying your crystal in herbs such as sage, sandalwood, frankincense, or myrrh can also help cleanse them. This has a lower cost and is gentle to your stones.
You can also bury them in the dirt. This method is used for deep cleanings. Simply dig a hole and place the crystal in with the point down, and cover. Place some kind of marker so you don't lose your stone. The amount of time needed is up to you and how you feel the crystal is recharging. You can also use flower pots for this as well.
However, the best, fastest and deepest way to cleanse or charge crystals is either by a professional mage or with a cleansing and charging pad