Sanskar
Chudakarana
The first haircut, a sign of leaving the old and beginning again.
When
In the first or third year, by family custom.
Chudakarana, the mundan, removes the hair of infancy. Many families offer that hair to a river or a tirth. A lock or a shikha is often left, according to the family.
A barber and a priest both have a part. Cleanliness, and as much assent as the child's age allows, belong to a careful house. Do not force it in a crowd.
This is a general introduction. Sequence, materials, and timing change with family, region, and shakha. Your priest and your own custom have the last word.