According to the preface, what is the most effective form of Guru service for attaining salvation, and how should it be performed?

The preface material detailed in Chapter 0 identifies the best and most certain service for achieving salvation as the writing of one's own Sadguru's biography. This act should be inspired either by the Guru's direct command or by a strong inner calling. The service extends beyond just writing; it requires personally studying the work regularly through practices like hundreds of readings (Parayans) and weekly recitations (Saptahs). For this service to be fruitful, it must be performed with a firm resolve, pure heart, excellent faith, selfless love, and unwavering devotion. This comprehensive service of body and speech is presented as a supreme path that does not interfere with worldly responsibilities.