American kids love to put their feet on chairs and tables. This is a major no-no in Europe.
Americans tend to talk loudly. Speak softly if at all on public transport.
In general, the Europeans are reserved and Americans tend to be gregarious. Don't mistake a "Resting French Face" for rudeness! If you greet shop owners and restaurant/café workers with a simple "bonjour/bonsoir" or hello in their language, they will be friendly and switch to English for you.
Restaurant/café tables and seating are small- your friends group going should adjust to the table/chair sizes NOT move chairs and tables so the whole group can sit at the table.
To go along with the small tables etc., don't ever lay your phone down on a table while you're eating or drinking. Someone could come and grab it on the way by and it's gone forever.
Restaurants often do not split the bill if you sit at a table together. Consider this before ordering.
Airplane Etiquette:
Middle seat gets both armrests
No photos that could include other passengers
Polite to all staff
Earphones for watching all videos. Download stuff on your phone just in case there are no TVs or they are not working
Quiet on a plane, especially if it is a red eye
Using a bathroom on a plane - what to expect, how to queue, etc.
Helpful gadgets for plane travel - earphones, neck pillow, eye mask, ear plugs, etc.
Deodorant is your friend while flying - good hygiene to be a pleasant neighbor for the flight
Anxiety can be normal for some folks when flying
Only take out what you need and put it away immediately after using. Avoid using the seat pockets so you don’t forget items when you deplane.
If you can, you should place their luggage in the overhead compartment in FRONT of you. If we have a short time between planes, you can’t go against traffic to get your luggage. If you are in row 20, your luggage should be in a row less than 20.