All positions of the planets favour the conducting of Upanayanam at the age of 8.The Upanayanam destroy boy's bad period.Upanayanam can keep at distance all the ill effects of the planets.
The boy symbolically accepts a spiritual teacher as father and the Vedas as mother and may get a new spiritual name.This ceremony is an introduction to the first of the four stages of life,that is "Brahmacharya Ashrama" (Studentship).
As per the tradition, an auspicious time and date is chosen for this and the boy is balded completely, leaving only a small tuft,called 'Bodi', in the center of the back-head.But nowdays,this is optional.
This is the last time a boy sits in his mother's lap and then the boy is handed over to his Guru.The Guru,after performing the rituals, whispers the Gayatri mantra,into the right ear of the boy and gives him the lessons of virtues and wisdom.This is the second birth for the boy.
Then the boy is supposed to beg alms from the people around in the ceremony.The alms are donated in the form of blessings,wheat, rice, sweets and in some cases,money or gold.The alms are handed over to the Guru.
Later on,the Guru hangs the thread (called Janeu-a thread spun by Brahmin girl and twisted by a Brahmin) on the boy(from left shoulder to the right waist,around the right hand).The thread is a symbol of 'Yajnopavita', means 'The thread of sacrifice'.
A Purohit(brahmin) should be engaged to teach 'Sandhya Vandanam',which the boy should be compelled to perform daily.'Sandhya Vandanam' should be performed in the morning and in the evening.'Sandhya Vandanam' performed at young age will bring him bright future.
The sacred thread used for this ceremony consists of three strands which are joined by a knot known as 'Brahmagranthi' or the 'Knot of Brahma'. The three strands represent the Hindu trinity-Brahma,Vishnu and Mahesh.There are many interpretations of the strands of the thread such as,Sattva,RajasTamas and Past,Present,Future.
Traditionally, the boy stays away from home to the teacher's Ashram(Gurukul) .Royal family members were also trained to live without luxury , in order to keep their minds pure and after marriage,they would remain attached to the spiritual values,the study of the Vedas and development of character,they learned in Gurukul.
It is required for marriage since it is assumed that such person must have undergone all the sacred oaths and must have led a bachelor's life and must have completed important education.
This ceremony is traditionally performed for boys,but there are epic references of women scholars receiving the 'Upanayanam Samskar'.As per the evidences,Sita of Ramayana,had performed the Sandhya puja (perfromed in sacred thread ceremony) and also recited the Gayathri mantra.But later on due to changes,women lost their right to perform this ceremony.