How can the pirates divide the treasure?

Two pirates want to evenly split the bag of gold coins they just acquired. The coins are all of equal value, and they initially figure they can just take turns removing one coin at a time. The problem with this method is that if the number of coins is an odd number, the person who goes first will always get the extra coin.

Without bothering to count the coins, what small modification can be made to this procedure so that if the number of coins is even they again each get the same amount, and if the number is odd, they each have an equal chance of getting the extra coin?