Out of your audience's view, secretly squeeze a large coin in between the fleshy part of your thumb and first finger.
Hold your hand out in front of you, as shown, at an angle that the coin is not visible to your specatators.
Push arm forward in a slight lunging motion and then pull back a little.
As you start to pull your arm back, curl first and second finger in to grab the coin between the two fingers.
Quickly uncurl the two fingers as shown.
When fingers are nearly uncurled, bring up thumb and smoothly push up the coin by pushing it flat against your first finger.
The coin is shown here pushed flat against your finger
Here is the audiences view of the coin which appears to have appeared out of thin air.
The above motions are all carried out when the hand is moving in a forward and then backwards direction to simulate a grabbing motion.
This trick benefits greatly from some practice in front of a mirror so that you can get an idea of your audience's view.