Signs to watch for include "postural signals" such as:
Tilting the head, neck sensitivity, inability to lie on their back, crying when moved out of their favorite sleeping position, difficulty in breastfeeding, limited motion (perhaps with a leg or arm), a bent body position, unusual differences in the appearance of one side of the body from the other (such as one hip being higher).
Because babies and children are less able to tell you exactly what hurts, you may find your chiropractic physician's skills especially welcome in being able to assess your child's overall health and physical structure.