This is a really good trick, all you need is a paper cup (the ones your drinks come in at McDonalds or Burgerking), and a pen .
The only pereperation you need to do is, hold the cup firmly in your hand.get the pen and pierce a wholein the cup with the pen.then chuck the pen away, you don't need it anymore.
Your ready to perform your trick. Hold the cup in your hand, show the audience its a proper cup, (making sure your thumb is covering the whole and remembering to keep the lid on the cup).Then hold the cup in both hands , (secretly slip your thumb into the whole.take your hands away from the cup and lift the cup up with your thumb.
TIPS: practice in front of a mirror befor performing this trick. Recomended time of practice is one day.