False Shuffle

Any shuffle that leaves the deck in the same order as it was before the shuffle.

A false shuffle at the right time can change a so-so card trick to a miracle. The type of shuffle depends on how much of the deck you're trying to "protect." For example, if somebody chooses a card and you secretly get it to the top of the deck, you probably want to protect the top card's position when you shuffle. For this, you can use an ordinary riffle shuffle. Just remember which hand is holding the cards from the upper half of the deck, and be careful not to release the last of these until all the cards in your other hand have fallen. Obviously you can use the same method to protect a card at the bottom.When you need to protect a larger number of cards at the top, the overhand shuffle is easier to use. Here's one method: Hold the deck in the usual overhand position (right fingers at the outer end, right thumb at the inner end, cards facing to the right). With your left thumb, pull off a bunch of cards that includes those you want to protect. Lift your right hand and bring it down to the left of the cards in your left hand. Pull off another bunch with your left thumb, and simultaneously grab the first bunch of cards between your right ring (third) finger at the outer end and the base of your right thumb at the inner end. Keep this grip as you lift your right hand for the next pass. You are now holding two bunches in your right hand--one between your second finger and your thumb, the other between your third finger and your thumb.
Shuffle off the cards in the bunch between your second finger and your thumb. Drop the remaining cards onto those in your left hand. That's it. Do it a couple of times. It's easy.

If you use a stacked deck, you need a shuffle that protects the order of the stack. But with many stacks, it doesn't hurt to cut the deck. For example, if thirteen cards are stacked A,2,3,4,5,6,7,8,9,10,J,Q,K, you can cut them as many times as you like and each card will still be 1 higher than the one to its left, with the understanding that A is 1 higher than K.
Here's a shuffle that merely cuts the deck: Hold the cards in your left hand. With your left thumb, push a batch of cards from the top into your right hand. *With your left fingers (not your thumb), push some cards from the bottom of the left cards to the top of the right cards. With your left thumb, push some cards from the top of the left cards to the bottom of the right cards. Repeat from *, moving cards from left top to right bottom and left bottom to right top until the whole deck is in your right hand. If you mention what you're doing (it's probably better not to), don't call it a "shuffle." Call it "mixing" the cards.
Here's another shuffle that does the same thing: It starts off like one of those described above. Hold the deck in the overhand position. With your left thumb, pull off a bunch of cards. Lift your right hand and bring it down to the left of the cards in your left hand. Pull off another bunch with your left thumb, and simultaneously grab the first bunch of cards between your right ring (third) finger at the outer end and the base of your right thumb at the inner end, and lift your right hand for the next pass. Your right hand is now holding one bunch of cards between your second finger and your thumb, and another between your third finger and your thumb. Drop the entire right bunch from your right hand onto the left side of the cards in your left hand. Lift your right hand and bring it down to the right of the cards in your left hand.
With your left thumb, pull off some of the cards in your right hand onto the right side of the cards in your left hand. Finally, lift your right hand and drop its remaining cards to the left of the cards in your left hand.
The last paragraph above describes the action that "cuts" the cards. If instead, you drop all the remaining cards onto the right side of the cards in your left hand, the deck will be in exactly its original order. This shuffle looks a bit skimpy. To pad it out, you can pull a few cards off the right bunch onto the right side of the cards in your left hand. Then bring your right hand over to the left and down, put your left thumb on it, and pretend to pull off some cards. Instead, just let your thumb slide over the cards. Lift the bunch over to the right and pull off a few more onto the right side. Repeat this until you've put all the cards on the right side.
Here's one more overhand shuffle that protects the entire order: With your left thumb, pull off about half the deck and then pull off 6 cards one at a time. Drop the rest of the cards to the left of those in your left hand, but "injog" them about an inch. That is, move your right hand about an inch toward you before dropping the cards so that there's a clearcut "step" between the two halves. Pick up all the cards to the right of the step, pull off 6 cards one at a time, and drop the rest of the cards to the left of those in your left hand.