1. Legally it is not the Tenants duty /liability to find a new Tenant for the Land Lord. This has to be done by landlord or agent-broker, in the same way, you become his tenant.
2. IF the agreement period has expired, THEN there is no need for any legal notice. You can just simply vacate and hand over empty possession. IF you are over-staying the agreement defined period, THEN you become liable for overdue rent amount at the discretion of the landlord.
Keep Smiling .... Hemant Agarwal