This tried-and-true effect is so old and tired that it is now considered suitable only for performance for children and heads of state. The effect is as simple as its name -- a coin is magically removed from a spectator's ear.
All a magician does to perform this effect is pick up a coin, reach over to the side of someone's head, stick the coin in their ear and pull it out. Because spectators don't know what the magician is going to do, they never think to look in the magician's hand. More daring magicians may, as an alternative, balance a coin on a spectator's shoulder as they walk by and then turn around, say, "Excuse me, there's something in your ear," then reach over, pick up the coin, and stick it in the spectator's ear. This is considered a "classier" method because it allows the hands to be shown empty, but since nobody is looking at the magician's hands in the first place, it's kind of pointless.
This trick was made famous in an episode of the old Night Gallery television show in which a magician accidentally loses a coin in a spectator's ear and the spectator goes nearly insane waiting for the coin to work its way out the other ear. The episode has a nice surprise ending involving the doctor finding a gigantic stream of ribbon.