Granite is an extremely hard stone and difficult to cut under any circumstances. It is not a good place to start for a novice stone cutter. For big jobs, power tools such as diamond saws will save a good deal of time and physical energy, and help you remove the bigger chunks of stone more efficiently. When working with a chisel, be patient, take your time and mind your technique to do the job well without injury. Small details may be difficult to achieve, so if want a precision finish, a less-difficult stone is recommended. Proper safety equipment is vital.
Mark the stone where you intend to cut using a pencil. The stone is porous, so do not use ink.
Put on your protective equipment, including goggles, dust mask and leather gloves. Granite chips can be very sharp, and silica dust released in the cutting process can cause lung problems down the road.
Begin to take out chunks of the granite, placing the edge of the chisel on the stone and striking the butt end with the hammer. Strike so that the force of the hammer goes away from you, both for safety and efficiency. Start well away from the positive area of your sculpture (the part of the stone that you want to remain) until you get a feel for it. For stronger strikes, place the chisel straight into the stone; striking at an angle is fine for detail, but it is hard to generate enough force to remove granite without hitting it straight on.
Cut in a line across the stone, removing a row of stone at time. Use the flat chisel to cut detail and level out the grooves. Carve your way towards your final sculpture, working all areas simultaneously.