Can you detail the specific method of service recommended by Dnyaneshwar Maharaj for acquiring knowledge from saints, as referenced in the book's preface?

Certainly. The Preface in Chapter 0 cites Lord Samarth Sadguru Dnyaneshwar Maharaj's commentary on the Shrimad Bhagavad Gita. His teaching emphasizes complete devotion as the path to knowledge. He advises that to bring knowledge into your mind, you must "serve the saints with your entire being." As quoted from Shri Dnyaneshwari, Chapter 4, this involves surrendering "with body, mind, and soul, at their feet" and performing "all service without ego." Through this selfless service, the saints will bestow enlightenment upon you, ensuring that doubts no longer arise.