In this study, a questionnaire was administered to student teachers and their teacher educators with the aim of gathering information that can be used to improve and strengthen the teaching practice program. The data were analyzed to make clear what factors aid teachers and student teachers when they are engaged in activities at the overall preparatory stages of instructional design. (1) Using factor-analysis, we extracted and interpreted 13 factors such as teacher's manuals for textbooks, organization of teaching, encouragement, and readiness, among others. After considering the correspondence between the extracted factors and the scripts of instructional design and preparatory activities, the factors were arranged and classified as follows: a) interpretation and understanding of teaching materials (teacher's manuals for the textbooks, textbooks); b) presentation (concretization) of teaching materials (encouragement, response and reply, studies of teaching materials, learning activities); c) structure of the teaching process (structure of teaching, simulation); and so on. (2) While engaged in instructional design, student teachers make use of only observable and prominent aids while teachers, on the other hand, use latent as well as observable aids in the whole process of teaching. Furthermore, there are common characteristics in terms of the kind of school. Namely, elementary school teachers and student teachers put emphasis on the predictability of children's learning activities, while junior high school teachers and student teachers place great importance on how to explain the contents of each subject. (3) The aids used by student teachers in each region and school are affected by their advisors there. (4) At the beginning of their teaching profession, teachers design instruction by focusing on presentation (concretization) of teaching materials. As they become more experienced, they learn to make substantial and worthwhile classes, going through almost all of the following processes: a) understanding the learners, b) structuring the teaching process, and c) adjusting and considering issues through (concrete) trial classes. These processes are all included in the scripts of instructional design.