Best thing to do is to Quarter it, separate the legs from the breast, split the breast in half.
cut down each side of the legs, popping the hipsockets and remove from carcass. There are two 'oysters' on the pelvis, very nice meat, remove also.
break the back off.
cut through on each side of the backbone on the breast and remove.
break the breast keel bone from the meat, including the cartilage and remove
cut through the breast into halves.
see http://www.smokingmeatforums.com/t/79898/cutting-up-a-chicken-part-1, just don't remove the wings or split the legs into drumsticks and thighs.