Position the coin in the palm of one of your hands, and use your thumb muscle in the base of your palm to hold it in place flat on your hand. Hold it naturally while avoiding showing the audience your palm so it doesn't appear like you're holding anything in that hand.
Show the audience your other hand is completely empty. Then put your empty hand into a fist and begin waving your other hand, palm facing down, over it. Make sure the coin is securely in the palm.
Turn your fisted hand so that your thumb side is facing up. Open your fingers slightly to allow enough space to deposit the coin into your fisted hand. Be careful to make this unnoticeable to the audience.
Pass your other hand over the opening of your fisted hand and release the coin as your hand comes in contact with the opening. Hold your pinkie and ring finger tight on your fisted hand to make sure the coin doesn't fall out the other side.
Snap your fingers and reveal the coin to your amazed audience.