This is often a problem for visitors to the U.S. In some countries the rules about titles and names are very clear. In the U.S. the rules are not always clear. If the person is the same age or younger,Americans usually use first names. Americans sometimes use titles and last names with their bosses, doctors, or teachers. They sometimes use titles and last names with older people, too. They usually don't use titles and first names. If you don't know what to call someone,you can ask. A good question to ask is, "What do people usually call you?" The person will either say,"you can call me Dr. Hull," for example. Or they might say, "Please call me Philip." Good luck!