Smoking has become socially unacceptable in the US, in part due to the health risks. Smoking is prohibited in government and public buildings, and many businesses, especially restaurants, will not permit smoking on the premises. Those restaurants that permit smoking will usually have a separate section for customers who smoke. Your school probably has a ban on smoking within campus buildings or near building entrances.
Tobacco products may not be sold to anyone under 18 years old, and federal law requires stores to ask to see a photo ID for anyone under 27 years old.
If you are a guest in someone’s home, you should ask whether it is ok to smoke before lighting up. If there are no ashtrays in the house, it is a good sign that smoking is not acceptable.
Smoking on airplane flights within the USA is prohibited. There are severe penalties for smoking on an airplane or in an airplane lavatory. Smoking is also prohibited on interstate trains and buses.
Smoking is prohibited on public transportation, including buses and trolleys.
Smoking around children is inappropriate. Buying cigarettes for a child, or giving a child a cigarette is illegal.
It is extremely impolite to blow smoke in someone’s face.
If you are smoking and someone coughs, it is often a polite way of asking you to extinguish the cigarette.