Americans tend to be on a first-name basis in the same general age group. So co-workers, classmates, and l and often caII each other by first names. But when you address doctors, lawyers, teachers, religious Ieaders and it's considered polite to use their last names with appropriate titles such as Mr., Miss, Mrs., and Ms. The titIe Ms. is used for a woman whose marital status you don't know (or who wants to hide her marital status). However it is impoIite to someone by the last name only. To address a man whose name you don't know, use sir. To address a woman you don't know, use ma'am. If you need to talk to a stranger for help or any other reason, it is good to begin your sentence with "Excuse me." This will show that you are polite and it wiIl heIp get the person's attention.