Do's and Dont's in your Country Καθημερινή ζωή και έθιμα

I was hoping to get a bit more knowledge into the "real" everyday life in different countries. Well... when/if we ever get back to real I was hoping anyway. If the zombie horde follows this or if a giant mutated dinosaur from Japan rises out of the sea then I just disregard.
In any event, I was hoping people could give a quick example that a foreigner may not know about social customs in a country that would be helpful to avoid embarassment or awkward situations. I was thinking about never ordering Ranch dressing on a Nicoise salad or never order ice in any drink ever. I will go first.

In this country, a major shopping center/store is called Target (target.com). Never... Never go to Target wearing khakis and a red shirt. You can thank me later.

Dont's: if you are a international student in China,don't call your professor or teacher by his or her name.Don't call elders by their name either, whoever you are.Both are considered impolite in China.If you are an international student in China, you should address your teacher or professor like this: Mr/Miss/Mrs/Ms + his or her last name, such as Ms li, Mr Liu, or Miss Yang.If you meet an old man outside, you should call him grandpa instead of calling him by his first name, so does an old woman.Don't wear a white hat when you go out. It is considered unlucky in China. You'd better not wear a green hat either. You'll thank me.

Do‘s😮n the bus, if you give your seat to the old people, you will be respected by everyone.

Eat schoggi its ok