Remove the majority of the grout that surrounds any one tile piece by holding a cold chisel at a slight angle to the grout and tapping the chisel with a hammer.
Tap the center of the tile piece from which the grout was removed with the hammer to crack the tile.
Position the chisel against a tile crack at a 45 degree angle, then tap the chisel with the hammer to break apart that piece.
Position the chisel against the bottom edge of any adjoining tile and strike the chisel with the hammer to break that piece away from the wall. Repeat this step for the remaining tiles.
Chisel away the underlying mortar after removing all of the tiles.