My wallet is bulky and full of cards I definitely don't need when traveling. Unless the airport really needs to check my library card... The smalles wallet for my id, card, whatever transport card I might need to purchase, and a couple of bills made all the difference when I try to fit everything I need throughout the day in a small bag that won't make my shoulder ache after 4 hours walking ahah, especially as someone who packs a camera, glasses, charger, etc.

Maybe a really basic tip but you never know what people remember or not!