Put on a respirator. This is key to keeping stone particles out of your respiratory system.
Place headphones over your ears and goggles on your eyes.
Place sturdy work gloves on your hands.
Turn on the saw and make a single cut across the width of the wall. You will want to press the saw lightly down the wall so that it makes only a guiding line. Then go over the line, pressing the saw into the stone wall more deeply until you have cut all the way through the wall.