After Gary gives 30 chest compressions, the best next step is to open the person's airway using the head-tilt, chin-lift maneuver, then give 2 rescue breaths. The breaths should be given by pinching the person's nostrils shut and sealing the mouth over theirs to blow steadily into the mouth for about 1 second per breath, watching for the chest to rise. After 2 breaths, continue with cycles of 30 chest compressions followed by 2 rescue breaths until the person shows signs of recovery or emergency help takes over.