I will second this advice. Particularly, the suggestion about scheduling the session when the child is well rested. That is not always a hard and fast time slot. Sometimes, you just have to admit that it's not going to work.
mikegreenwald wrote:
I have rarely had trouble with the kids, but frequently with parents or other interfering adults who try to manipulate the children. A careful instruction with adults present is needed before starting to shoot. As with all other portraiture, complete familiarity with your equipment is essential, and means for distracting the subject (child) and keeping them happy and occupied. Schedule the shoot at time when the child is well rested. Sleepiness is impossible to overcome.