What is described as the most effective form of written service for attaining salvation, and what does it involve?

According to the source, the best and most certain written service for obtaining the fruit of salvation is to write the biography of one's Sadguru. As detailed in Chapter 0, this should be undertaken either by the Guru's command or through inner inspiration. The service extends beyond writing; it also involves personally studying the biography regularly, performing hundreds of readings known as Parayans, and conducting weekly recitations called Saptahs. These acts must be done with a firm resolve, pure heart, selfless love, and unwavering devotion to be spiritually fruitful.