From time to time, the ritual tools we use need to be cleaned. Not physically cleaned, but magickally, as the energy we channel and use slowly builds up and either "flavors" the continual use of the tool or begins to hinder our ability to channel magick with it. This happens with man-made tools as well as with natural items such as stones, feathers, and crystals. While there are numerous ways to cleanse your ritual tools, these are the methods I most commonly use.
Fire, Earth, Air, and Water: You can use Elemental energy to cleanse an item, but use your common sense. You wouldn't want to run a feather through a candle flame or emmerse an item in water that could be damaged. Choose the Element of your choice and connect the tool to the Element (pass it through a candle flame for Fire, sprinkle it with soil for Earth, wave it through sage or cedar incense for Air, or submerge it in a cauldron full of Water). As you do, visualize the layers of old energy being washed, buried, blown, or burnt away. Simple maintenance just before Beltane and Samhain each year will keep your tools functioning well.
The Power of Nature: Set stones and tools in the sunlight (either outside or in a window sill) and let the natural energy of the sun slowly clean them. Leave stones in the rain, or outside for a full moon cycle. By the time you use them again, they will be clean. But if you make use of natural energy this way, make sure that you give something back to the natural world.