Did you see David Blaine twist his arm 360 degrees? Well, he did not invent that trick. Actually it's pretty simple and a rather old trick.
WHAT YOU'LL NEED:
-You have to wear a long sleeved shirt.
WHAT'S THE SECRET?
It may seem like you're just placing your hand on the table, but in reality you're doing a secret move - you're twisting your arm before placing your hand on the table. (The long sleeve while hide the twist.)
Twisting your hand requires some practice, but anyone can do it: Put your right hand on the table and have your fingers pointing towards your body. You should have your fingers pointing to the left. Now turn your palm up, while still having your fingers point left. Now turn your hand over the same way once more, until it is face down again. (You'll get the hang of it.)
PERFORMING THE TRICK:
Put your hand on the table/sidewalk: Tell your volunteer from the audience to do exactly what you're doing, and begin to slowly twist your arm COUNTERCLOCKWISE.
When your fingers start to point to the left, distract him from what you're doing. Say something like "you're doing it wrong... do exactly what I'm doing!" or "Maybe you should back up a bit to get a better view of my directions." Point to his hand or maybe push him away a bit with your other hand, and do the secret move while he's concentrating on himself.
If you wear long sleeves, it will look like you're just compfortably resting your hand on the table, with your fingers slightly to the left. But in reality you will be quite uncomfortable, because your hand is really twisted 270 degrees to the left. Your volunteer won't know that. He'll just put his hand down normally.
Now, when you start moving your hand, you will simply be un-twisting your hand back into it's normal, compfortable position, while your volunteer is actually trying to twist his arm around in a rather unnatural fashion. He won't be able to imitate your move.
PS: You can also add some sound effects... Simply tuck a plastic cup in your armpit, and gently press on it as you twist your hand. It will sound like bone crunching.
You can find more detailed instructions and supplies for this and many other typical Street Magic tricks here.