In the U.S., U.K., and most Western countries, men should remove their hats (including baseball caps) when attending church services, at funerals, and during the singing of the national anthem.  Unfortunately this simple act of courtesy is often ignored, especially by younger people, and it does cause offense to many.

A gentleman would never wear a hat inside a building, and a guest who walks into someone's home wearing a hat is considered a buffoon whose parents did a bad job of educating their offspring - for it rarely rains inside a house!

I actually heard this one on National Public Radio years ago.  The French are not rude. Rather they believe anyone who smiles a lot is an idiot.  If you want to relate to the French, smile with your eyes, not with your lips.

In England the day after Christmas Day is called Boxing Day (December 26th).  In Victorian times this was the day when every child was expected to put one of their Christmas presents into a box to be given to a poor child.

In Germany a gentleman stands behind a lady on an escalator going up, and in front of her on an escalator going down - just in case she stumbles.  It is also a lot more fun!

The gesture that many Americans think to be universal to indicate "OK" or "I agree", that of the fingers spread with the tips of thumb and index finger forming a circle, is obscene in many countries, notably Brazil.   

When doing business in London, it is OK to drink yourself silly at lunch (as long as your business partners are doing the same thing), but if you fall and black out afterwards, you are less likely to accomplish your goals than if you had stayed upright.

Some interesting things to consider if traveling to Africa. I spent some time in rural Zambia and noted that: Women can walk around  with their breasts exposed but do not expose their legs in public. Men typically wear shirts even in the hot weather, it's perceived that you are very poor (can't afford a shirt) if you are shirtless.

Do NOT bring wine to dinner at the home of a French person; such an act is thought to evidence a lack of confidence in the host's wine choice.  Flowers are more appreciated.  

I think the most important thing when honoring guests from foreign countries is to accept and understand the differences.  Do not react to something that is different to what YOU would do.  

In most Muslim Countries and in India, you should not eat with your left hand or shake hands with someone with it.  That hand is typically used for potentially unsanitary reasons.  It's embarrassing to find this out the hard way.

When in Scotland please remember "Scotch" is the drink and "Scots" are the people.

Here are some of the differences I have personally experienced between Norwegian and American cultures:  

• Norwegians are for the most part dressed in business casual at work, and dress up more formal when going out for dinner.
  
  

• If served Aquavit, do not drink it as a shot - even though it is served in small shot-glasses - take only small sips.  
   

• Cheeses like Mozzarella and Monterey Jack are sliced with a cheese slicer; don't cut it with a knife.  
  
  

• Unless someone else gets up; be seated until dinner is over.  Mingle AFTER dinner.  
  
  

• Norwegians don't ask for a "doggy bag" at a restaurant.

The Dutch find the English and American telephone manner to be very rude. It is not only polite, but standard in Holland for a caller to begin by stating who they are.

"This is (my name). I would like to speak to..."  And not just "Hello, could I speak to..."

I hear comments about the rudeness of my friends calling from England or the USA all the time. Even those I deem to be educated and polite people, manage to offend the Dutch, simply by not mentioning their own name at the beginning of the conversation.  It simply isn't done!

Never take white lilies to an English Lady or white chrysanthemums to a Japanese Lady - they are the flowers of death and will not be seen as a compliment.

In Western Europe Peacock feathers inside a house, or opening an umbrella inside a home, guarantees bad luck for the owner of the home.

Shooting off firecrackers on New Year's Eve is the Chinese way of sending out the old year and welcoming in the New Year. On the stroke of midnight on New Year's Eve, every door in the house, and even windows, have to be open to allow the old year to go out.

Letting an Arab see the soles of your shoes is an unforgivable insult.

Making the sign of Peace (forefinger and middle finger open in the shape of a "V") is fine in Britain, Australia and New Zealand, unless you lift your hand to do so with your palm up - then you are achieving the same result of an American giving someone "the finger".