The first haircut
The first haircut is quite an important thing in many world cultures and religions. It is treated as one form of rite of passage.
In Mongolia children get their first hair cut when they are between 2 and 6 years old. According to lunar calendar boys do it in their even year and girls in their odd year.
Orthodox and Hasidic Jewish boys get their first cut when they are 3 years old. In Yiddish this ceremony is called the "upsherenish" or "upsherin" (shear off). In Hebrew people call it "halaqah" (smoothing). The child's side locks or "payot" are traditionally left intact.
For the members of Hasidic community, the upsherin is the event that also means the start of the formal educational system and the beginning of Torah study for the male child. Boys now wear a "yarmulke" and "tzitzis".

yarmulke cap
Yarmulke or kippah (kappel) is thin, a bit rounded skull cap traditionally worn by Jewish men. In some Conservative and Reform communities it is also worn by women. The cap is a symbol of respect for God.
Tzitzis or tzitzit are "fringes" or "tassels" worn by observant Jews on the corners of four-cornered garments, including the "tallit" (prayer shawl). They are worn only by men.

tallit prayer shawl
Many non-Hasidic and non-Orthodox families also observe the tradition of cutting the hair of their son for the first time when he is three years old.
Some boys in Israel get their first haircut on the holiday called "Lag Ba'omer". The event is held in the tomb of Rabbi Simeon bar Yohai located in the town of Meron.
In Turkmenistan a child's first haircut is performed by mother's older brother or, if she does not have one, by another male relative. The ritual is believed to provide a protection for the child. The first haircut is done on child's first birthday.
Exceptions are situations where a younger sibling has died or mother has recently suffered a miscarriage. Then everything is delayed until the birth of next child. Mother traditionally put some hair of her older child to the garment of her baby.
In Hinduism it is believed that there is a connection between the hair from birth and bad habits from past lives. There is a ceremony called "Mundan" or "Choodakarana" ("Chadakarana") or "Chaula". It is a rite or "saṃskāra" when babies get their first haircut.
It is done when the child is 1 or 3 years old. The hair is shaven. But sometimes not completely. The "shikha" (also known as "choti" or "bodi") is a tuft at the crown of the head. That hair is left as it is believed that the shikha protects the brain.
Some believe that the Mundan ensures a long life, better future and also protects the child from the evil eye. The Mundan is regarded as an act of cleansing the body and soul. There are also beliefs that this ceremony ease troubles associated with headache, pains when child gets first teeth etc.

Mundan rite
What's the procedure during the Mundan? The priest or sometimes the father performs it. The mother sits with her child facing west of the sacred fire. The priest chants and shaves off part of child's head. The rest is shaven by a special barber.
After the shaving is done the head is washed with holy water ("Gangajal") and a paste of turmeric and sandalwood is applied. The hair that was shaven off is offered to gods or to the holy river like for example Ganges or Ganga
Some decide to perform the Mundan on the banks of the Ganges river. Many go the famous pilgrimage city of Rishikesh (Hrishikesh) in the Indian state of Uttarakhand located in the north of the country. The special Mundan ceremony or "chadakarana sanskara" is performed there.
In the ceremony trained priests, "acharyas" and "rishikumars" chant Vedic mantras and prayers. The hair shaven is offered to the holy Ganges river. The child and her or his family perform a "yagna" ceremony and the "Ganga Aarti". Ganga Aarti is a ritual worshipping the Ganges or Ganga river. Yagna or Yajña is a ritual of sacrifice performed to please the gods or to express certain personal wishes.