This two‐year qualitative participatory research project examines practical guidelines for supervision. Sixteen experienced supervisors across professional settings of family therapy, child protection, and specialty mental health services in the geographical regions of Northern Norway and Northern Sweden outline four main practical guidelines in supervision based on their supervisory practices: (1) elaborating an agreed‐upon contract; (2) exploring potential formats; (3) exploring contents; (4) acknowledging responsibility for process and dilemmas. Participants summarised how they generated mutual growth in supervisory relationships, while being respectful of the first‐person perspective of supervisees. The study challenges pre‐dominating guidelines about deficit‐ or developmental stage‐oriented supervision. It illustrates reflecting processes and a polyphonic orientation in supervision by welcoming diversity, wondering, and tolerance for the not‐yet‐decided among involved persons in a mutual exploration and calibration of relevant knowledge. It outlines a dialogical research for sharing, exploring, and questioning knowledge as beneficial for whom, told by whom, and evaluated by whom.