As the earlier example demonstrates, the format of a diary can be predetermined but very often you will need to amend this based on the reaction of participants to your design. The example I gave of my experience was unique in that I had an opportunity to discuss the diary format with participants and I had time to amend and reconstruct the diary to suit individuals. You will not always be in this position; comes to have the diary returned you have harvested the type of data you need in a way that can be analysed