What cleansing is actually doing
Most guides will tell you that cleansing clears stagnant or foreign energy from your cards. That claim is unfalsifiable, and this site is not going to make it. What is observable is more modest and, honestly, more useful: cleansing is a boundary ritual. It marks the end of one thing and the beginning of another, and it moves your attention deliberately onto the deck before you ask it anything.
That matters more than it sounds like it should. A reading done while half-distracted produces a half-considered interpretation. A short, deliberate act beforehand (any act, consistently applied) is a reliable way of arriving properly. Whether you believe anything is leaving the cards is beside the point; something is changing in you, and you are the instrument doing the reading.
Sorting to order: the method that does the most
Take the deck and put it back into its original sequence, Fool through World, then each suit Ace through King. It takes about five minutes and it is by far the most valuable cleansing method, because it is the only one that also teaches you something. You handle every card, you see which ones you have forgotten, and you notice the ones you flinch past.
For a new deck this is close to essential, and not for ritual reasons: it is how you find out what is actually in the box. Decks vary, some renumber Strength and Justice, some rename the suits or the court cards entirely. Sorting is how you meet a deck rather than merely owning it.
Knocking, shuffling, and breath
Knocking once on the top of the stack is the fastest reset there is, and it is what most working readers actually do between clients. Some tap three times, some rap the deck against the table edge. The mechanism is attention, and it takes two seconds, which is precisely why it survives in real practice while more elaborate rituals get abandoned.
Shuffling with deliberate attention (slowly, without a question in mind, until the deck feels settled) does the same job with more contact. So does simply holding the stack and taking a breath before you begin. If a method is so involved that you skip it when you are tired, it is doing less for you than a knock you will actually perform.
Smoke, moonlight, crystals, and salt, with the physical warnings
These are the methods that get recommended most and scrutinised least, so here is the practical side. Incense or herb smoke works fine for the ritual, but it leaves residue that dulls gilded edges over time and can yellow white borders, pass the deck through quickly rather than holding it in the stream. A crystal placed on the stack is completely harmless to the cards, which is a genuine point in its favour whatever you believe about it.
Moonlight is the popular one and it is safe in itself, but the windowsill is not: overnight condensation warps card stock, and cards left until morning catch direct sun. Salt is the method to actually avoid: it is hygroscopic, meaning it pulls moisture toward whatever sits in it, and buried cards come back subtly warped and pitted. If you want the salt ritual, put the deck in a sealed bag inside the bowl. And never use direct sunlight, which fades ink permanently, reds and yellows first.
When it is genuinely worth doing
The moments that come up repeatedly in real practice: a new deck, a reading that landed heavily and that you want to close properly, after someone else has handled your cards, and returning to a deck you have not touched in months. Each of those is a real transition, which is exactly what a boundary ritual is for.
What does not hold up is a fixed schedule. Cleansing every Sunday because a guide said so turns a deliberate act into a maintenance task, and a maintenance task performed without attention is doing nothing at all, which brings you back to the honest version: the ritual works to the exact extent that you are actually present for it.