When you arrive at a meeting, do you greet everyone as a group or greet each person individually? If someone gives you something, do you wait or open it when you receive it? Is it good to burp after a meal?
It is very funny to see different ways when we look at each culture in detail.
In a TESOL classroom, we will face challenges because it is an intercultural class. People from different cultures learning a target language, and try to adjust their behavior for the benefit of the group, or sometimes for individual goals. As instructors, we need to be aware that there are differences in manners and that they can be shocking sometimes. We need to learn how to be tolerant and understanding persons. However, I think that we can establish some general rules to facilitate coexistence. For example, seeing your cell phone or your laptop while someone is talking to you is it disrespectful or not so important? If someone in my class were doing this, I would think that he or she is not interested in learning, or that I´m not engaging enough. It is important to be objective, and do not make wrong attributions because what is disrespectful for me may not be for others. But we can agree on some rules that do not generate discomfort. These can be about arrival times, class interruptions, and dressing.
It´s important to get to know our students, their cultures, and involve their parents during the process. If a problem appears due to a misinterpretation of manners, parents and teachers can solve it together and avoid the disagreement.
In general terms, in my culture we have a high tolerance for emotional expressiveness, we are polychronic, so we value more the personal relationships over agenda, and we consider disrespectful belching in public or leave the plate with food after meals (although this may vary in subcultures.) Entering or leaving the classroom while the teacher is talking is not well seen either. There is a great article about our Argentine manners here: https://culturalatlas.sbs.com.au/argentine-culture/etiquette-1b7ca7cb-bf45-425e-909e-b15c4f4456ae
Now I know many more things of my culture that I did not know because they are part of our unconscious behavior. Each instructor must know the differences to avoid misunderstandings and wrong judgments.