Miss a few days and sometimes the practice of writing a journal can be lost for the entire trip so try to make a notation daily, no matter how small. Writing every day, even small details, will help you maintain your momentum.
Allow lots of space between points so you can keep track of how your itinerary changes as you travel. Rough out your itinerary in a few pages at the front of your journal. It could be the classic Moleskine Notebook or one that is a little more fun such as I Was Here. I like a notebook and pen as the information will never be lost with a technology change and the journals look great on your shelf. This is a fun and inspiring travel journal.
