This paper presents an innovative and useful methodology to analyze instructional talk. In teacher education, there is a lack of practical methods that the tutor teacher can use to discuss and reflect on student teachers' lessons. The student teacher cannot remember what actually happened during the lesson, and the feedback and discussions are based on memory and are, therefore, unstructured. The purpose of this explorative and descriptive case study was to characterize the teacher talk used in the process of a teacher's guidance of secondary school students' acquisition of knowledge about physics. First, a classification method for classroom talk was developed. Then, using this method, the pattern of teacher talk and the dependence of the patterns on teacher expertise are described.