I travel journal! It's something I do after my trips as it would take up too much time out of my actual travels, and it's a nice way to go back and remember it afterwards. I usually write quick notes to myself on my phone while I'm traveling so I don't forget stuff and can capture how I was feeling in that moment, and then I'll go through these notes when I'm actually journaling and make it more coherent.

I also consider it vital to collect ephemera when I'm traveling - tickets, museum maps, a paper napkin printed with the restaurant logo, etc. It gives me things to stick in alongside my writing and helps bring the page to life. Nothing is trash when you travel journal!

I also have a portable printer (HP Sprocket) which I use to print out photos to add to my pages. It makes all photos a uniform business card size, so it doesn't take up too much space on the page and looks cohesive.