If you have lost your birth certificate in India, the first step would be to contact the local Municipal Corporation or the Tehsildar's Office in your area. You can also reach out to the local police station for help. You may be asked to provide proof of identity and residence, so make sure to have those documents ready. Additionally, you will need to submit a written application as well as any other documents that may help verify your identity. Once the authorities have verified your information, they will help you obtain a duplicate birth certificate.