According to the source, what is considered the most effective form of Guru service through writing, and how should it be performed?

As detailed in Chapter 0, the best and most certain written service for attaining salvation is to compose the biography of one's own Sadguru. This should be done either by the Guru's command or from a deep inner inspiration. The text emphasizes that this act must be performed with a firm resolve, a pure heart, excellent faith, selfless love, and unwavering devotion. Furthermore, this service includes the personal and regular study of the biography, performing hundreds of readings (Parayans) and weekly recitations (Saptahs), and encouraging other devotees to do the same.