Poorly designed diagrams reduce the effective teaching and learning of mathematics. Typical problems include graphic elements that do not focus on mathematical concepts and their relations. Through the development of series of diagrams to support the teaching of simple geometric concepts, a user centred design method has been developed, which when used in conjunction with guidelines on gestalt principles and critical information cues, helps students to structure and visualise concepts, thereby facilitating learning. Although the diagrams produced using this method did not show a significant quantitative improvement in students' learning, they were shown to encourage reflection on the underlying concepts. Educational diagram designers also believed such a method would enhance current design practice.