Say “please” and “thank you” when you ask people for something / when you ask people to do something for you (at restaurants and at work).
When someone bumps into you say “sorry”, if they get mad say “sorry” (some people will cause a scene if you don’t just apologize).
Say “excuse me” when you want to get through a big crowd, when someone is standing in your way, or when you accidentally bump into someone.
Don’t call people “ma’am” unless you’re in the South, because they may think you’re implying they’re old and get offended.
Hold the door for someone if they’re right behind you (don’t let it just slam in their face).
Shake hands with people when you meet them at work encounters when you introduce yourself.
Always be nice to people, and don’t take it to personally if they’re not nice back.
Try not to chew with your mouth open. It’s seen as rude and/or gross by most people.
Don’t look at/stare at people for too long. You’ll creep them out or think you’re judging them.
Cover your mouth if you sneeze or cough.
Wash your hands when you go to the restroom. This one seems obvious, but there’s a lot of people who don’t, and people who do wash their hands will judge you for not washing your hands (mainly because it’s gross).
We don’t really have much etiquette other than that. Just be a descent human being and you’ll probably be fine.