My aunt is one of those people who can talk to anyone about anything. If she goes to a party where she doesn't know any of the people, she just walks up to the first person that she sees and introduces herself. And yet she doesn't seem to talk about deeply important things like politics or religion. She always starts off on something very obvious like the other person's job. Very soon she's talking as if she's known the other person for years. I asked her once what her secret was. She said that the most important thing in a conversation was listening. People love to talk about themselves, so if you allow them to do so, it's very easy to keep a conversation going. You have to listen very carefully and ask questions. And you have to look interested, too. So don't keep looking at other things in the room while you're talking to someone.
Another thing that I've noticed is that she only pays people compliments. She says: “I like your hair. Which hairdresser do you go to?” or “You look very well. Have you been on holiday?” Friendly messages like this seem to provide an easy way into a conversation.