According to the preface, what is the best and most certain method of serving a Guru through writing?

The preface suggests that the best and most certain service in writing that grants the fruit of salvation is to write the biography of one's own Sadguru. As detailed in Chapter 0, this service is not merely the act of writing itself. It must be accompanied by personally studying the work regularly, performing devotional readings (Parayans) and weekly recitations (Saptahs) with a pure heart, excellent faith, and unwavering devotion. This form of service, combining body and speech, is considered highly effective and can be performed without conflicting with one's worldly or family duties, making it a supreme path to spiritual attainment.