Zac Poonen emphasizes that Spirit-filled service is characterized by being a love-slave to God, recognizing our debt to others, acknowledging human insufficiency, and fulfilling God's specific calling. He illustrates that true service stems from the understanding that we belong wholly to God, and our motivation should be love for Christ rather than personal gain. Poonen highlights the Apostle Paul's example of being a debtor to share the gospel, his humility in recognizing his weaknesses, and the importance of seeking God's direction in our unique callings. Ultimately, Spirit-filled service is about yielding to God's will and being ready to bless others with the message of salvation.