Ritual Salt Bath for Tarot Cards
There are a variety of reasons to cleanse a tarot deck, or in fact any magickal object. In this case, I had treated a deck carelessly, and it had a negative energy as a result.
Wrap the tarot deck you wish to cleanse in a soft cloth. Bury it in a clean, nice container with enough salt to cover. The principle behind this is that crystals are magickally absorbent, and thus draw the energy out via reverse osmosis. Salt is just a very cheap, disposable crystal.
After I did this, I requested the help of the Goddess in blessing the deck, who through me called to the Spirits of the Watchers of the North, South, East, and West (in that order, which matters), and lit a cone of myrrh incense (though any pleasant and benevolent offering would do) for each one. At Her instruction, I asked that they bless the deck, and blew out all of the cones together, letting them burn until they extinguished themselves. I stayed in the room while they burned, to experience the aroma in the company of my Goddess.
Let the cards remain until you have achieved the desired result. Note: When I tried this, I left the cards in for too long, and they were entirely drained of all energy, including the minimal energy they came with from the retailer. If I were to need this in the future I would leave them for only 24 hours or so, most likely. It's not the end of the world, as I know how to recharge the deck.