What should a rent agreement include?
The parties, the property, rent and deposit, term and notice, who pays what, and how it ends — in writing, signed by both sides.
At minimum: the full names and addresses of both parties, a clear description of the property including what is let with it, the rent and the date it falls due, the security deposit and the terms for its return, the term of the agreement and its start date, and the notice period for either side to end it.
Then the clauses that prevent arguments later: which bills the tenant pays and which the landlord pays, who handles maintenance and repairs, whether the rent escalates on renewal and by how much, any lock-in period, whether subletting is permitted, and the landlord's right to inspect with notice.
Both parties should sign every page, keep an original each, and attach an inventory of fittings and appliances with their condition. An agreement that exists only as a conversation is the one that ends badly — the written version is what either side can actually rely on.
General information about renting in India, not legal advice. Rules differ by state — check with your local Sub-Registrar office or a lawyer before acting on this.