The easiest way to pit cherries is with a cherry pitter, a handy gadget available at kitchen supply stores. Here's how to use one:
Wash and drain the cherries well in a colander. Remove the stems of cherries -- simply pull them off the fruit.
Place one cherry, stem end up, into the center of the open-hole tray of the cherry pitter.
Holding the pitter over a bowl, squeeze the handles of the cherry pitter together, and allow the pit to fall into the bowl.
Remove the pitted cherry from the holder, and repeat as needed with the remaining cherries.