We use the commands "sit" and "stay" and sometimes even "down" for certain pictures. They are command words we use pretty much everyday and everywhere so to take pictures has become a snap.
lots of treats for good paricipation too. And when we wan her to tilt her head, while shes sitting we ask her "whos the good girl? are you the good girl?" in a high pitched voice and she tilts her head at us then we tell her shes the good girl and we give her a treat.. When she was younger we just waited till she was tired to take come of our best pictures.
Good luck!