I'm from Taiwan, but I live in Bost

I'm from Taiwan, but I live in Boston now. I'm a student at a language school.I live with an american family. They're very nice and very friendly,and I am comfortable there. I have just one problem: when they introduce me to people, I don't know what to call them.My American family says the new person's name, but they don't say what title to use. Do I call them "Mr." or "Mrs."? How about "Miss"or"Ms."? Then, do I use their last name or their first name? Please help!