What are the primary methods described in the preface for devotees to engage with a Sadguru's teachings and serve both the Guru and the wider community?

Chapter 0 outlines that a Sadguru accepts service from devotees through books. Devotees can engage by either having the Guru's biographies written or by studying these works. The core community practice described is performing Parayans and Saptahs of a detailed poetic Guru biography. This act serves multiple purposes: it is a form of Guru service for both the writer and the readers; it constitutes service to God in humanity (Jan-Janardan) and public service; and it helps the devotees achieve the purpose of their lives. For followers of Sai Baba, the 'Shri Sai Satcharita' is presented as the preeminent work for this form of devotional engagement and community building.