The diagnosis of psychological issues requires a careful and structured approach. The diagnostic process is the foundation for successful counseling and treatment. At the same time, clinical decisions regarding diagnosis, the collection of relevant life history data, and the clarification of motivation and therapy goals present significant challenges in the initial therapy sessions, where it is essential to establish a trusting and constructive therapeutic working relationship. The authors demonstrate how the diagnostic process can be successfully structured in a practical and application-oriented manner. This makes diagnostic approaches and methods tangible and individually adaptable. The initial conversation serves as an important diagnostic approach, along with the selection and application of various diagnostic tools such as diagnostic interviews or symptom-specific scales.