For these to be effective, it is suggested that you read about Playing Card Systems first. In every feat below, the deck is assumed to have been legitimately shuffled by the audience first.
If you have a group of friends with whom you regularly get together to play cards with, you probably shouldn't perform any of these feats for them.
As you have the cards selected, simply link the appropriate card images together. If you are using the Dominic playing card mnemonics, you would simply link the person who represents the first card with the action that represents the second card. If this is done properly and effectively, then when any given card is named, it will be a simple matter to recall your link and name the other card.
It is best to practice by starting with a smaller amount, say 10 pairs of cards, and work your way up gradually to all 26 pairs.
To perform this, have an audience member remove a group of cards (not more than a 15 or 20) from the deck face down. you are going to look at the remaining cards one at a time, and mentally mutilate, in some way, the image for each card as you see it. If, for example, you're using the Bob Farmer playing card mnemonics and you see the 2 of clubs, you might mentally burn up a toucan. If the next card is a 5 of diamonds, you would then picture a burning fiend, and so on.
Once you have gone through your portion of the deck, simply mentally go through the deck in order, and look for the cards which you don't remember mutilating. If you're mentally going through the clubs, you might remember having mutilated your images for the Ace, 2, and 3 of clubs, but not remember multilating your image for the 4 of clubs, then you state that you don't remember seeing the 4 of clubs.
To make this more effective for multiple performances on the same day, it's best to use one method of multilation for each performance, and change the multilation method for later performances. Your first performance might employ the burning of all the card images, while a second performance might use a breaking in half of all the card images.
One intriguing way to present this is to have the entire deck dealt out into four 13-card hands, as in Bridge. You would look through 3 of the Bridge hands, which are chosen by your audience, and then recall which cards you haven't seen yet, and are therefore in the fourth hand.
As you go through the deck, one card at a time, you link the image for the position to the image for the card. If the first card is the queen of hearts, then you would link your image for the queen of hearts to your image for 1. The next card would be linked to your image for 2, and so on.
This feat takes more practice than most of the others, but it is one of the most impressive demonstration you can do with a shuffled deck of cards.