copying shape keys

ok so i made a head and am trying to get it to do different expressions. I tried rigging it but i could not get it to work. now i am trying it with shape keys but am having trouble getting both sides of the head to do the same thing. if i make the right side of his mouth smile is there a way i can copy it so the left side of the mouth will make the same smile shape?

When modeling try using x-mirror option in tool menu (T in 3-D view) if you are looking for an expression that it’s symmetrical. Cant help you with copying mirrored shape keyes.