This paper reports on the implementation of a guided note taking strategy to promote Thai students' understanding of electromagnetism during a lecture course. The aim of the study was to enhance student learning of electromagnetism concepts. The developed guided notes contain quotations, diagrams, pictures, problems, and blank spaces to encourage student interactive engagement with the lectures. The guided note templates were critiqued by a group of experienced university physics lecturers and piloted with graduate physics education students to check the content validity. Over 300 first year university students (aged about 18-19 years) attended lectures that did not involve guided note taking. Six hundred students participated in the guided note taking approach. Students' understanding of electromagnetism was investigated using a conceptual test. Comparison of the pre- and post-test results of the two groups of students indicated that students who were involved in the guided note taking approach performed better on the conceptual test than students who were not involved in this approach. From interviews, it was found that students viewed the guided note taking approach as a supportive tool that helped them concentrate on the lecture. Promoting student involvement in the lecture class through the process of guided note taking was shown to be a meaningful learning strategy for first year university physics classes.