In this paper we present accumulated results from two years of experience with a teaching unit on debugging Java programs. With this special teaching unit, we strive to foster the debugging skills of our students. Students were asked to find different defects in given code, to analyze these and finally to fix them. As well, students were requested to document their approach in writing. The achieved results ranged from “all bugs found and fixed” to “completely lost in the code”. When analyzing these results, we discovered that the debugging skills of our students seem to correlate with some non-technical skills that are essential base competencies in software engineering, such as the ability to work in a systematic way. This implies that for improving our students' debugging skills, it is helpful to address not only the technical aspects of debugging, but to foster the required base competencies as well.