How can devotees build a community and engage in service based on a Guru's teachings, according to the provided preface?

The preface suggests that a powerful way to serve a Guru and build a community is through the study and devotional reading of their biographies. Chapter 0 explains that a Sadguru accepts service from devotees through books, either by writing great works themselves or by having their biographies written. When devotees study and perform Parayans (devotional readings) of a detailed Guru biography, the writer performs Guru service, and the other devotees participating also achieve the purpose of their lives. This communal study is presented as a form of public service and serving God in humanity (Jan-Janardan).