Secret:

Use "Feel the Heat" or the "Classic Force" to lose a card in the deck. If you don't already know these easy ways to find or force a card, then use the left naviagation and for goodness sakes, go learn them! They are also both pretty easy magic tricks to learn.
Look through the deck and grab 4 indifferent cards as well as the selected card.
Place the selected card on the bottom of the stack of these five cards.

Place the cards between the first knuckles of the audience memeber's outstreched fist. To make sure you know exactly where to place the cards, I will try to explain a little further.
If someone was going to punch you with their fist, and this was all going in slow motion, you could fit cards into their fist. Just imagine yourself sliding in the cards between the cracks in their knuckles. This is where the cards go. (Easy so far?)
Count to three "One, Two, Three!!"
Slap the cards like you were giving someone five. Smack! The bottom card is the one that will stay in the fist. You have to hit it fairly hard, but still be gentle.
Obviously, this is one magic trick you will have to practice on yourself to get both the right fist tension and the slapping motion down. But in reality, it is a pretty easy magic trick to do.
Turn over the last remaining card. Is this it? Hopefully you can come up with a better saying for this trick like!
THIS IS AMAZING! THE ONE FINAL CARD REMAINING IS MIRACULOUSLY YOUR CARD WHICH WAS ABSOLUTELY LOST IN THE DECK! I SWEAR IT HAS GOT TO BE A MIRACLE! WOW!
This is a perfect trick to teach to kids because it involves some action, some complexity, but it really is pretty simple and easy to do.