1. the NATO alphabet. (Alfa, bravo, charlie, delta…) It's surprisingly easy to memorize: it will only take you a few sittings of practice. And it's useful, for when you need to turn letters into words. And then people cutely wonder if you're ex-military.
2. I tie a small ribbon to my luggage. It could be anything: string, tinsel. If you're familiar with wine glass charms, same idea. It makes the bag identifiable from distance, so long as the charm is in line of sight. It does not, remarkably, stop strangers from grabbing the wrong bag, but it does get funny if they insist they recognize their bag when you ask them "you tied sparkly pink ribbon to your bag?"