This card trick is completely awesome. There is no set up needed and it will blow your friends minds.
Step 1: Dealing
Say to your audience "I'm just going to deal you out some cards" so it sounds like you are giving a random amount, but really you will be counting out 13 cards.
Step 2: Spliting
Tell your audience member to take any amount of cards away from the pile of 13 as they want. Tell them to put the card they take away to the side for now. In this example 7 cards were set aside.
Step 3: Counting and Memorizing
Tell your audience member to shuffle the remaining am out of cards as much as they'd like. When they're done tell them to memorize the bottomed card. Now put the pile on the top of the original deck.
Step 4: Making the Clock
Make a clock as shown in the picture. Start with 12 and work your way counter clockwise to 1. Lay down the cards from the top of the deck.
Step 5: More Counting
Bring back the pile of cards that your audience member set aside earlier. Ask them to count how many cards there are. Then go on the clock and flip over the number that matches the amount of cards. for example 7 cards would be 7:00
The card you flip over will be the card that they had memorized!
Enjoy impressing everyone you know.