Beliefs help shape how teachers perceive effective mathematics teaching. Providers of professional development, be they local or from other countries, need to be cognisant of such perceptions. This paper seeks to answer the question, "What do South African teachers perceive as effective and ineffective teaching for developing conceptual understanding of mathematics?" A sample of 46 mathematics teachers was shown vignettes from eight different classrooms where the lesson dealt with some aspect of teaching fractions, and were then asked to comment on the strengths and weakness of what they observed. The comments were classified into seven themes with 18 sub-themes or categories. The majority of the comments focused on two themes, use of materials and modes of instruction. The various mathematical approaches for developing the concept of fractions received little attention. Perceptions of which vignette was considered to be the most effective approach to teaching mathematics resulted in a wide variety of responses. Finally implications for professional development are explored. It is suggested that in-service courses should be geared to what teachers themselves consider best practice, and that reflection on practice should play a more significant role in professional development.