You do not need to master every custom. A few observant habits communicate respect immediately.
When giving or receiving something in a formal or respectful moment, using both hands—or supporting one forearm with the other—shows care.
Subways, residential lanes and shared indoor spaces often reward a quieter voice. Watch what people around you are doing and follow the tone of the space.
At train and elevator doors, stand aside, allow people to leave and then enter. It is simple, efficient and appreciated anywhere.
A bow can range from a small nod to a deeper formal gesture. For a visitor, a natural nod with a polite greeting is usually more respectful than exaggerating a bow you do not understand.