Reader, beware!

I have gleaned these rules through decades of trial and error. Since it is considered “impolite” to ask about directly, I can only guess at these rules.
Most rules may only apply to white American males between twenty and forty years old -- since this is the only experience I have.
These rules should be taken very seriously if you want to be respected in middle-class American society. Outside the United States and/or the middle-class, there are entirely different rules.
Many of these rules are arbitrary, wasteful, or downright dangerous. If you find a rule truly disagreeable, find a way to hide what you really do and pretend to obey the rule. For instance, sticking things in your ear canals is dangerous. But I still tell people I put q-tips inside and “clean” my ears.