1) When someone shows you a photo on their phone don't swipe left or right. You never know what's next!
2) Don't call someone more than twice continuously. If they don't pick up your call that means they have something more important to attend to
3) Never order the expensive dish on the menu when someone is treating you for lunch/dinner. If possible ask them to order their choice of food for you.
4) When a group changes topic after your enter, leave immediately. Better not to disturb them.
5) Respect Everyone: When you respect everyone without caring about their economic status. You get respect from everyone.