The following is a description of how I cleanse my crystals. There are plenty of methods out there and you are welcome to research more into it. Everyone has their own way of doing things, as it should be. This is the method that works for me and you should find one that works for you. 

I use crystals in a lot of my healing rituals. In the past, I've also used crystals as my shields.

For both uses, I cleanse my crystals before and after use. First, I will explain how I cleanse them. Then I will explain how I use them in healing and shielding.  

I collect crystals. At the moment, I don't have very many. But my goal is own 50-100 by the end of this year. I get them from various sources: Ebay, Etsy, local metaphyscial shop and even in trades/swaps. Before I use them, I cleanse them of any negative or stagnant energy that may be attached to them. I actually have 2 processes that I use, depending on the sitution. If the crystal is new to me, I use a month long cleansing ritual. If I've had it, and want to reuse it, I have a simple ritual that I use. 


For one that I aleady have and have gone through the month long cleansing, I place them in a bowl of sea salt overnight. The next morning I flush the salt in the toilet. For me, the salt absorbs any old, stagnant energy. The flushing of the salt symbolizes flushing of the old energies. If you want, you can also place it in the Earth over night. The Earth will absord the energies just like the salt. The next day, the crystal is cleansed and ready to use. 
 

For newly obtained crystals, my cleansing ritual is a bit more involved. No matter when I get it, I wait until the night of the Full Moon to start. I dig a hole in the Earth and place the crystal inside then cover it up. The hole doesn't have to be huge--just big enough to fit the crystal.I leave it in the ground until the next Full Moon.     Be sure to take the crystal out the morning or early in the day of the next Full Moon. Place it in a bowl of salt water in the sun. Be sure it's not directly in the sun--in the sun light is good enough. If left in direct sunlight, a bad reflection can start a fire. Leave it in the sun light all day. Also leave it under the light of moon that night. The next day, the crystal is ready to use!! 
 

 
 

How I use my crystalsFor healing, I use crystals in 2 different ways. I rub the crystal over the part of the body that is bothered while visualizing it absorbing any negative energies. I've used to it help clean out muscle aches and pains, headaches, cramps, general body aches, etc. Another way to do it is to visualize healing energies into the crystal. I then give the crystal to the person who needs it (or if it's for myself). I instruct them to place the crystal on the area of their body that is bothering them. Then they are to visualize the crystal absorbing the negative energy.   

For shielding.

This one may take a little practice to do. It took me about a month to finally get a good shield in one. The shield can be used for anything-- negativity, bad work being used against you etc. To work a shield into a crystal, I get myself into a meditative state while holding the crystal in my dominant hand (the hand you write with). I visualize a white light going directly into the crystal. (you can use any color you want) I usually do this for about 15 minutes. Sometimes, one ritual is enough. Sometimes it take a few more tries. Once  I feel as if my shield is strong enough, I then keep it on myself at all time. You can carry it in your pocket or out it in an amulet bag. Or if you want a more permanent type, you can wrap it in wire and wear it as a necklace!!