1. Don’t wear jeans, sneakers, bear hide mantles, or the cloak of displacement
2. Don’t do the American lean against a wall while clutching the Monster Manual
3. When speaking with a local, don’t assume they know common or elvish or that they have the helm of comprehending languages magic item
4. At bars, do not wrinkle your nose in disgust at what’s on tap and ask if they have anything American D&D like Arabellan Dry or Arkhen’s Hoard
5. Ask for the WC or toilet and not the bathroom, chamber pot, or castle garderobe
6. Tipping is not customary so unless the service is extraordinary, do not leave gem dust, small baked goods, or a mummified goblin hand for services rendered
7. Don’t make eye contact with and smile at every stranger like you are a 20 charisma bard
8. Don’t loudly boast about the second amendment, looser weapon ownership laws, and how you’re touring around packing heat with your morningstar, halberd, and warhammer
9. Don’t lack awareness of your surroundings and loudly announce to your travel party that the pickpockets can successfully rob you if they roll an 8 on sleight of hand
10. Don’t carry everything you own while sightseeing like you’re preparing to fight a mindflayer
11. At restaurants, don’t hand the menu back to the waiter and vaguely gesture towards the kitchen asking them to whip up chopforest or kender stumblenoodles
12. Don’t shrug and say you have no idea what universal health care is, you just usually take a short or long rest depending on how many spell slots you have remaining
13. Don’t stand staring at a thousand-year-old structure and compare it to a 20-year-old hovel near Phandalin, where you’re from
14. When you are given the price of something in euros, don’t ask the conversion to gold pieces or if you could barter with a leatherworker’s kit or prayer beads of the dawnmother
15. Bottom line: Don’t be a typical American barbarian. Save your rage for dealing with customs on the way home.