American society seems to be much more informal than the British and, in some ways, is characterized by less social distinction. Students do not rise when a teacher enters the room. One does not always address a person by his title, such as "Major" or "General" or "Doctor" in the case of a holder of a Doctor of Philosophy degree. The respectful "Sir" is not always used in the northern and western parts of the country.
However, it is best to use a person's title when first meeting him/her, and then allow the person to tell you how he/she wishes to be called.

They use first names when calling each other, slap on the back, joke and are much freer in their speech, which is more slangy than the conventional British English. You will often hear the word "Hi" (a form of greeting among friends) used instead of the usual "Hello," and "Howdy" instead of "How do you do?"
Those who don't easily show these signs of friendship are called "snooty" or "snobbish." In contrast, people who show such simple signs of friendship, particularly to their own economic and social inferiors, are praised as "regular guys," or as "truly democratic." As a description of character, democratic is generally used to signify that a person of high social or economic status acts in such a way that his or her inferiors are not reminded of their inferiority.

Yet, in spite of all the informality, Americans, even in the way they address each other, show consciousness of social distinction. For example, one is likely to use somewhat more formal language when talking to superiors. While the informal "Hello" is an acceptable greeting from employee to employer, the employee is more apt to say "Hello, Mr. Ferguson," while the employer may reply "Hello, Jim." Southerners make a point of saying "Yes, sir," or "Yes, Ma'am," or "No, sir," or "No, Ma'am," when talking to an older person or a person in a position of authority. While this is good form all over the United Stales, "Yes. Mr. Weston" or "No, Mrs. Baker" is somewhat more common in a similar situation in the North or West.
Certain other forms of politeness are observed on social occasions. Women may wear hats in church. in restaurants, and often when attending luncheons in public places and other public social functions except those that take place in the evening. Men who do wear hats ordinarily remove them in elevators, churches, restaurants, private homes, business offices — in fad, in most public situations when they wish to show respect.