How to make character arms/head aim up/down following crosshair?

Hello

This thread has been created b4 but the link seams to be dead

In any third person shooters (as well as FPS) when a character looks up, or looks down, the character models obviously 'animate' along with the direction the player is looking. How would you implement this? The way I thought about it was to have the arms and the head rotate when the player aims up/down but I'm not sure if that would work or if there's a better way