I like that this most relaxed and easy of definitions is by Emily Post, the queen of American etiquette for the past 100 years.  She was known, as are her descendants, as being easy going, unpretentious and utterly unimpressed with showy displays of so-called etiquette.

Think about those around you and try your best to make them comfortable and cared for. Try your best to not purposely offend them or hurt their feelings.  Do those things and most any other issues of etiquette and manners will take care of themselves.

That means you have to pay attention and be humble about your own status and knowledge, especially when traveling to foreign countries.  That includes traveling across town in many cases!

Drawing © Marty Coleman 

“Manners are a sensitive awareness of the feelings of others. If you have that awareness, you have good manners, no matter what fork you use.” – Emily Post, 1872-1960, American author and etiquette expert.  
Some things to note:  Post was a divorced single mother, a pretty rare and sometimes shameful thing back in the 1800’s.  She started writing after her sons were grown up a bit, publishing first at the age of 32.  Her famous book ‘Etiquette’ did not get published until she was 50 years old.