Place a quarter in the palm of your left hand.
Hold a pen in between the thumb and pointer finger of your right hand while keeping the rest of your fingers relaxed and loose so you can catch the quarter.
Bring the tip of the pen down toward your palm.
Flick your left hand up quickly and slightly as the pen comes toward your hand, causing the quarter to fly up toward your other hand. Make sure you do this when your hands are close together so you can catch it easily and it is unnoticeable.
Catch the quarter in your right hand as the pen taps your left palm. Turn your left hand over so they can see it isn't behind your hand.
Remove the pen cap and shake it out into your left palm.
Drop the quarter from your right hand into your left hand as you do so to make it appear that the quarter was inside the pen cap.