I traveled around Europe for a month in 2005 and it was the first time to travel by myself.
I packed a empty sketch book and colour pencils in my backpack and kept a travel diary.
It was just for killing time as I was alone and had much enough time to keep it especially when I was waiting for a coach or train. I collect train tickets and museum tickets, flyers and receipts for collage and stick them with drawings on the pages.
This is much better than taking pictures as I started to observe things carefully, for example details of buildings or artworks in the museums.
Since then, i always bring the diary when I go for a travel and this became like my lifework.