Describe the different kinds of Guru service discussed and explain why some are considered limited or worldly.

Chapter 0 outlines several forms of Guru service. One type is worldly service, which involves writing biographies of great figures like politicians, warriors, or jurists. This is considered limited by space and time, rooted in self-interest, and does not yield eternal spiritual fruits. A higher form of service is writing the biographies of many saints, which does yield spiritual fruits but is still considered partial or one-sided. The text also describes direct service to saints, as taught by Dnyaneshwar Maharaj, which involves surrendering at their feet with body, mind, and soul to gain knowledge. Finally, the most certain service is writing the biography of one's own Sadguru, which is considered a complete path to spiritual attainment.