TL;DR: Valid Indian Will - 5 Essentials
A Will (also called a Last Will and Testament) is a legal document that expresses how you want your assets distributed after your death. In India, Wills are governed by the Indian Succession Act, 1925 for Hindus, Buddhists, Sikhs, Jains, Christians, Parsis, and Jews. Muslims follow the Muslim Personal Law for inheritance, with some limitations on testamentary freedom.
Dying without a Will (intestate) means your assets are distributed according to personal law - which may not reflect your wishes. Writing a Will ensures your family knows exactly what you intended and reduces disputes. It is one of the most important legal documents an adult can have.
A Will is valid in India if: (1) the testator is above 18 years of age and of sound mind, (2) it is signed or thumb-printed by the testator, (3) it is attested by at least two witnesses who sign in the presence of the testator, and (4) no witness is a beneficiary named in the Will. Registration is optional but strongly recommended.
For Hindus, Buddhists, Sikhs, and Jains, the Hindu Succession Act applies alongside the Indian Succession Act. A Hindu can Will away self-acquired property freely but has limitations on ancestral property (HUF property). Muslims in India have more restricted testamentary freedom - a Muslim can Will only up to one-third of their estate to non-heirs; the rest is distributed according to Islamic inheritance law.