One of the best ways to elevate small talk into interesting conversations is to ask questions. Stick with more general questions to learn more about someone without being invasive.
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Even if you make seemingly innocent assumptions, they can lead to embarrassment for both yourself and your new acquaintance. For example, when meeting a younger woman and an older woman, you might think they're mother and daughter. But assuming so (and asking about it) could lead to quite an awkward situation if they turn out to be sisters, dating, or just friends. Go with a more general "And who is this?" rather than "Is this your daughter?" and save yourself an embarrassing situation.
The Art of Small Talk: 5 Questions Never to Ask [The Art of Manliness]