According to the source, what is the most effective way to express unwavering faith and devotion to one's Sadguru through service?

As detailed in Chapter 0, the best and most certain service to express unwavering devotion is to write the biography of one's Sadguru, prompted either by their command or by inner inspiration. This act of service is most fruitful when accompanied by the personal, regular study of the biography. The text encourages performing hundreds of readings, known as Parayans, and weekly recitations, or Saptahs, with a firm resolve, pure heart, and selfless love. This form of service, combining body and speech, is presented as the supreme method for attaining salvation without interfering with one's worldly duties.