This paper presents two studies in which an empirical approach was taken to understand and explain form generation and decisions taken in the design process. In particular, the activities addressing aesthetic aspects when exteriorising form ideas in the design process have been the focus of the present study. Diary methods were the starting point of this research for investigating the form generation process through collecting self-reflective comments from the participants. The main focus of this paper is to address potentials and limitations of the three variants of diary method used for data collection, namely, unstructured diaries, structured diaries and visual diaries. A set of method evaluation criteria was developed to compare the structure of the diary variants. By qualitative analysis of the results and comparison of the diary variants, strengths and weaknesses of each variant were identified. One of the prominent factors in the diary variants was pegged to be due to the logging delay after the occurrence of the activities. (Contains 6 figures and 5 footnotes.)