You can be silent for a moment, and let them pick up the conversation. Or you can say, “This is awkward because I can’t think of anything to say.” But over time you can develop many different things to ask about. For example, “Do you have siblings?”, “Where did you grow up?”, “What are you working on?”, “What do you see yourself doing in ten years?”, or “Do you have any interests outside of work?” Alternatively, you can tell a story about something that happened to you recently.