Eye Contact

In the United States, most people consider it polite, and a demonstration of sincerity, to look each other directly in the eye, at least in intervals, when having a conversation.  It is considered very rude and in some cases may be interpreted as threatening to look continuously at someone or stare at someone unless you are engaged in conversation with that person.  It is as rude to stare or comment about someone's body in America as it is anywhere else.

Greetings/Parting Company

Generally, when people who are not well acquainted with each other meet or part company, it is considered polite to shake hands. Refusing to shake an offered hand is likely to be interpreted as rude. When shaking hands, a firm but not tight grip is prefered. Simply placing your hand in the hand of the other person is considered to be an ill mannered and insincere handshake.

Table Manners & Restaurant Etiquette

When dining, people consider it rude for a guest or dining partner to belch or burp, eat with an open mouth, smack, or lick your fingers.  Napkins, generally provided are available at every meal and should be placed in ones lap and then used throughout the meal to clean ones fingers and mouth.

It is acceptable to refuse additional servings of food by saying "No, thank you" and the host or hostess will not be insulted if you do so. Similarly, if you leave a small amount of uneaten food on your plate at a restaurant or in a home, it is not considered an insult. If you eat everything on the plate, a host or hostess may possibly feel that they have not prepared enough food and might be embarrassed. People in the United States serve and eat food with either hand, but never take food from a communal serving dish with their hands. Generally, a serving utensil is used.

Americans typically use forks, spoons and knives to eat, but there are some types of foods that are accepatable to eat with one's fingers, like sandwiches or pizza. When in doubt, look to see what others are doing. In formal dining situations, if you wonder whether or not it is acceptable to begin eating, you should wait until the oldest woman (or oldest man if no women are present) begins to eat. When eating, do not pick up the bowl or plate from the table to hold underneath your mouth. Even noodles, soup, and rice are eaten with the plate or bowl remaining on the table. When consuming soup and hot liquids, it is considered impolite to slurp-do not do thisl When consuming noodles, twirl them around your fork and then put it in your mouth.

If you are eating in a restaurant, you will be expected to add a 15 to 20 % tip for the server to your bill. In America, wait staff might occasionally stop by your table to ask how your meal is, which is considered good service. They will also bring you your check when it seems reasonable that you are finished with your meal, however this is not necessarily an indication that you must leave right away (Do not be too embarassed to ask for the check either: waiters and waitresses cannot read minds.) Take your time to finish your meal, and unless there is a line of people waiting at the door, it is not considered rude to linger at your table for as long as you like.

Bar & Nightlife Etiquette

If you are in a pub or bar, it's customary to leave a small tip on the bar for each drink ordered (usually around $1 each). If you plan to have several drinks you can leave your credit card with the bartender for future rounds (commonly called "opening a tab"), and then pay for all your drinks when you are ready to leave. Just make sure you let the bartender know which people or drinks you intend to pay for on your card, or you might end up buying drinks for more people in your party than you intended. 

Also, if someone that you just met offers to buy you a drink (especially for women), it can be interpreted as a "pick up" -- in other words, an indication that they find you attractive. You may always turn down a drink that is offered to you by saying "no, thank you" or indicate that you're already attached to someone, and it is advised to do so if you are not interested in unwanted attention from the person who is offering it. If you accept the drink, you are not obligated to the person who offered it in any way, but they might reasonably expect some pleasant conversation from you while you are drinking it. It is also considered courteous to offer to pay for the next  drink if someone else pays for yours, and this is a nice way of leaving the encounter neutral, neither indicating that you are attracted or not attracted to the person offering it, but that you are on friendly terms. If a person in a bar is rude to you in any way in this type of situation, you may simply excuse yourself and are not obligated to continue conversing with them.

Entering/Leaving 

When entering or leaving a building, people in the United States consider it good manners to hold open the door for people who are exiting or entering behind them. People also wait for an elevator to empty before they enter.  It is considered to be very rude for people to push past one another to enter a building, train car, or subway car, and especially rude to make physical contact with a stranger while doing so.  On elevators or moving sidewalks, it is polite to stand to the right and walk to the left. While standing in a line, don't stand too close to the person in front of you.  People can be sensitive about their personal "space." Walking in front of a person, particularly when space prevents leaving at least 2-3 feet, is considered rude.

Cell Phones

When making or receiving a call in a public place, with the exception of some public transportation, it is polite to move away from people who can hear the conversation.  It is seen as very inconsiderate to carry on telephone conversations in a loud voice in public, in particular restaurants, offices, museums, and shops. In places like theatres, concerts, or cinemas it is customary to turn off one's cell phone altogether: patrons who do not abide by this rule may be asked to leave, and management will not refund your ticket..

Lining Up (Forming a Queue)

In the United States, forming a line is most common for counter service where food, tickets, or services must be bought and multiple people must be served at once. It is customary to form a line in front of the register and wait one's turn to be served: pushing past others and jostling in a free for all is not acceptable, nor is cutting in front of someone who is waiting.

Smoking 

Only about 20% of the American public are smokers according to the latest 2012 data.  Smoking bans and restrictions vary state by state and area by area but there are some general rules.  Twenty seven states ban smoking in all enclosed places.  That includes airports, hotels, stores, concert halls, etc. with some exceptions.  For example, cigar bars obviously allow smoking.  The states that do not ban smoking do allow local entities to restrict smoking.  Always look for and follow the signage.  Americans have little tolerance for smokers who violate the smoking bans due to concerns about second hand smoke dangers.  Smokers are also often restricted from being within 15 feet (4.5 meters) of an entrance to a building.  So smokers often are found standing some distance from an entrance smoking.  American smokers almost never walk while smoking.  Walking with a lit cigarette is considered rude.  People in the USA are not expecting someone to be carrying hot embers at a child's face level and if you are walking with a cigarette you may find you have burned someone.  Always ask if it is ok to smoke in a crowded area before lighting up.