I have an old friend that was brilliant at the art of conversation. He always said it was because he was a master of the obvious. Sometimes the easiest way to break out of a conversation rut is to talk about things that are right in front of you or you already know to be true. Talk about your day, the location you are at, even the weather. Comment about something interesting the other person is wearing and take notice if your mate did something different (like a haircut). If your partner brings up a topic, listen and ask to know more about that. It may seem silly at first, but it is a proven method to get the ball rolling, which is something even us couples need every now and then.