Again my apologies if this does not belong here.
Also, please note the disclaimer at the beginning, and that I again am probably no expert, just an enthusiast and hobbyist.
Caring for your crystals
Similarly to our own bodies and varying energy systems, crystals occasionally require a cleansing. They can, with frequent use or via ambient absorption, accumulate an excess of energies that could be either harmful to the stone or detrimental to its usefulness as a tool, however you may use it. This excess is best removed in some way, lest the crystal's function continue to be impaired, or the build-up of unwanted energy cause damage to the stone itself.
There are many methods possible for cleansing a stone, which I will attempt to cover as thoroughly as possible;
Salt water cleansing
Cleansing stones with salt water is one of the most common methods that I have personally heard of for cleansing; it is fairly easy, and I do commonly use it myself in the winter when nothing else is available. However, it comes with a warning; be VERY CAREFUL when using salt water cleansing, as some stones are easily damaged by this harsher method. Be sure to research the physical properties of the stone you intend to cleanse in this manner; if you're not sure, try searching online or asking somewhere (such as a forum), or checking a resource such as a book on crystals, to make sure that this method of cleansing won't damage the stone. A good guide to the physical make up of stones that I recommend would be the National Audubon Society’s “Field Guide to Rocks and Minerals”, as well as Melody’s “Love is in the Earth”.
Common sense will take you fairly far when trying to determine which stones can and can't be cleansed in this manner, but the phrase "if you aren't sure, don't do it" is still VERY important. There are other methods if you aren't sure. Some of the stones that I am personally aware of that do not benefit from this type of cleansing are some of the more "fibrous" ones; such as some forms of calcite, selenite, etc. Softer stones are also at higher risks. The salt can get into the pores of the more porous crystals, and can harm the surface of some of the more polished ones, eventually dulling the finish, so I can't state this enough; be careful!
Now, on to the actual method!
First of all, the obvious; get some salt. If you aren't lucky enough to live near a naturally salty body of water, then you're going to have to make some. I highly recommend sea salt, if you can get it; preferably non-iodized salt. This is usually fairly easy to obtain, as most supermarkets carry it, and it's price is usually similar to that of regular table salt. This is also often referred to as Kosher salt. It usually says right on the package whether or not it's iodized, but be careful; not all sea salt is non-iodized. It is fine, however, if you can't get anything other than table salt. The effects should be similar, if not the same; I personally try to remain as close to nature as possible.
Now use whatever salt you've gathered to mix up your salt water; try not to use too much salt. The exact amount is not important; your intent and care while cleansing is the most important. However you should use common sense; try not to use more salt than your amount of water can absorb.
Once you've mixed up your water, you're ready to start the cleansing! There are a few ways to do this, and none of them are wrong; if you feel that you have a different idea, try it out! Experiment a little, modify these methods, but always keep your intent on clearing the crystal.
One method would be to soak the crystal in the salt water for a few hours. I would keep this salty water out of direct light, to decrease the chances of damage to the stone, while it is soaking. It is best to cleanse one stone at a time with this method; using multiple stones in the same water may result in a muddled cleansing, or not much of a cleansing at all, as the water may not be enough to do a thorough clearing out of the stagnant energies.
Another method would be to simply wipe the surface with your fingertips as the crystal is submerged in the salt water; focus your intent as you do this, and imagine or visualize, however you are comfortable, that you are literally wiping away the collected impurities. Other similar methods would probably work just as well; remember, experiment!
Once you have completed using the salt water cleansing, make sure to rinse your crystal with running water, until you are satisfied that any of the remaining salt water has been washed away, enjoy! You may want to re-dedicate your stone if you had originally done so, just to make sure its purpose has not also been cleansed away!
Alternative salt cleansing method
This method is something that I stumbled upon while researching more information about salt water cleansing; it is a little easier, and definitely much safer for the crystal itself. Simply gather a sufficient amount of salt to bury your stone, and do so; leave it buried for about a day or so, though if you feel it needs to be submerged longer, then by all means do so. This source, however, stresses that you should not re-use this salt for anything else after the cleansing; the salt, which is also a crystal itself, most likely has absorbed whatever negativity it has cleansed, and you wouldn't want to invite that back into your life i most cases.
Once the cleansing is complete, you might want to run it under some water for a moment, simply to clear off whatever salt may remain.
Source: http://www.thesoulelement.com/cleansingcrystals.htm
(Just checked and the source link is broken. My apologies, I'll have to shore that up later somehow)
Water Cleansing
This method is as easy as it may sound; it is very similar to the salt water cleansing method, or at least it can be. You can hold a crystal beneath running water, keeping in mind the intent of cleansing the crystal; it may help to visualize the water clearing away whatever negativity is within the crystal, washing down the drain with the water.
This method is usually used in a pinch, when one doesn't have the time for a potentially deeper cleansing method, however. I use this method quite often myself, but I have noticed that it required frequent follow-up treatments if I didn't use a "deeper" method.
This method carries the same warning as the salt water cleansing method... be VERY CAREFUL when using water with some stones, as it may damage them. It is less likely to be severely damaging if it is simply water, but once again, if you aren't sure, don't do it.
You can also, as I have learned during research, use running water in the form of a river, stream, waterfall etc; simply hold the stone in the flow of the water and once again concentrate on the water washing away the negativities that have built up within the stone. Make sure you don't drop it!
One tip for cleansing with running water is to attempt to use as pure a source of water as possible. Try to avoid water that is potentially full of chemicals or other impurities, if at all possible. If you have to use bottled water, then do; though that water is generally considered stagnant, and you may want to charge it in the sun or moonlight before use.
Smudging
This is a method that has been reputed to have been used by Native Americans for ages; I can't confirm whether or not this is true, but I'm sure some simple internet research will yield some good results.
To smudge, simply hold the stone within the smoke from burning incense; it helps to research the more metaphysical properties of the incense you want to use, finding one that works with your purposes and intentions. There are many sorts of incense, though there are certain types that are historically known for their cleansing properties; such as frankincense, sandalwood, sage, etc.
And that's that method... fairly simple, and fairly cheap, as incense is usually readily available for low prices and in large amounts.
Light Cleansing
This method is a little more energy focused. For those of you who work with energy, you may or may not be familiar with this method, used for other purposes such as healing.
To use this method, one usually visualizes a white, cleansing/healing light; I personally find it easiest to imagine this light as being centered around my hands and fingers, pouring through me via the top of my head or thereabouts. It is also a good idea to shield yourself if you intend to open yourself up to these energies; if you are not very well versed in methods of shielding, it might be a good idea to research them before beginning. You may also want to ground yourself, and make sure that you research this as well if you are unsure; you don't want to take the negativity that you intend to clear from the stone into yourself; you want to ground it.
Once this white light has been established to your liking, you can use it on the crystal; hold it in your hands or hold your hands above it, visualizing the light washing away the collected negativity within the stone. Once you feel that the stone has been cleansed, make sure that you ground this cleared negativity, as mentioned above.
The sun
This method is also fairly simple; place your crystal in an area where it will catch the maximum amount of sunlight throughout the daytime. Let it soak up that sunlight, an excellent natural cleanser! However, this method also comes with a warning; some crystals, such as quartz, may catch and magnify the sunlight, possibly causing burns in the carpet/room, or even a fire. So make sure you keep an eye on that crystal throughout the day!
There is also one more warning associated with sunlight cleansing; some crystals, such as amethyst and citrine, will fade with excessive exposure to the sun. If you intend to cleanse these using sunlight, do so sparingly; one day of cleansing should be alright using this method, but continued exposure(s) to the sun may cause significant fading of the the crystal, and thus it's usefulness. It's best, once again, to research and use common sense if you are unsure.
The moon
This method is just like the sunlight method, only later in the day. In fact, if you wish, you could leave a stone in an area where it will collect sunlight AND moonlight, giving it a more energetic AND relaxed charge.
Some of the best times to do this type of cleansing are, obviously, at the time of the full moon; the waning moon, however, has been said to provide a good sense of removing negativity (source: http://www.neatstuff.net/avalon/texts/know-how.html)
The Earth
This is a wonderful method for cleansing, and easy enough for most people to conduct; the earth is, after all, everywhere.
To utilize this method, bury your stone in the earth, leaving it there for 24 hours or more. It is best to bury it in the actual earth itself, such as in your yard; the physical connection with the earth and its energies can act as a powerful cleanser and charger. If it is not possible to do this, it is acceptable to gather some fresh earth for this purpose; I highly recommend gathering this earth the day you intend to use it, and I STRONGLY recommend returning it to the earth once the cleansing is complete, so that the "tainted" earth may also be cleansed. Keeping this earth and even planting something in it may result in the proliferation of this negativity.
I personally do not recommend potting soil, unless it is also freshly bagged in such a way that you can be sure of where it came from and how it was processed; the idea with ALL of these methods is to avoid chemicals and impurities within the earth you use to cleanse with, and many topsoils are treated with fertilizers and other chemicals. Avoiding this as much as possible is highly recommended.
This method of cleansing also carries a warning; some stones may be damaged by this direct contact with the earth in similar ways to the salt water cleansing. It has been suggested via various resources that the stone may be wrapped in a natural material such as cotton or linen before it is buried, to avoid direct contact with the soil. Personally, however, I believe that this wrapping can detract from the actual cleansing power, and it is difficult to get natural fabrics that are truly natural and un-treated.
Other Crystals
There are some crystals that naturally function as cleansers, and thus never (or almost never) require cleansing of their own. With these crystals, all one has to do is place the crystal that they wish to cleanse onto the cluster or crystal they wish to cleanse with; leave it there for approximately 24 hours, or until you feel that the stone has been cleansed to your liking.
Some sources site that any cluster of crystals will suffice for this, and if you intend to use any cluster of crystals in particular, I would recommend dedicating it for that purpose before you use it, to ensure that the job is getting done as efficiently as possible.
One of the natural cleansers that I personally use and hear the most about are citrine clusters, preferably natural citrine. It can be difficult/expensive to get a natural citrine cluster, as much of the commercially sold pieces of citrine is artificially treated quartz or amethyst, and not as powerful as the natural product. The natural crystal tends to be darker in color than the artificial version, and natural clusters are usually comprised of smaller crystals, at least in the less expensive pieces.
This concludes the collection of methods that I have either used or run across via my own research. I hope this helps, and if anyone has another method that they use of have heard of, I'd love to hear it! :3
Please feel free to ask questions or point out errors!
