The samskara
Namakarana is the naming samskara, traditionally performed on the eleventh or twelfth day after birth, though many families now hold it in the first three months. It is the point at which the child formally receives a name and is introduced to the household deities.
How the syllable is chosen
Each of the 27 nakshatras is divided into four padas, and each pada has an assigned syllable. The child's janma nakshatra and pada — determined by the moon's position at the moment of birth — give the syllable with which the name traditionally begins.
For example, a child born under Rohini pada 2 has the syllable "Vaa"; Ashwini pada 1 gives "Chu". A purohit will compute this from the birth date, time and place. This app computes the janma nakshatra automatically when you add a family member with their birth details.
Many families give two names: the rashi nama based on the nakshatra syllable, used for rituals, and a vyavaharika nama used in daily life. Both are entirely acceptable.
What happens in the ceremony
Punyahavachanam purifies the space. Nandi Shraddha invokes the ancestors' blessing. The father or grandfather whispers the name into the child's right ear, and it is then announced to the gathering. Madhu-prashana — a touch of honey applied with a gold ring — follows. The ceremony closes with the cradle ceremony, in which the child is placed in a decorated cradle while the women of the family sing.
Preparing
Confirm your gotra and pravara with elders beforehand — the sankalpa requires them. Keep new clothes for the child and the parents, honey, and a gold ring. The paternal aunt traditionally has a role in the cradle ceremony.