I've said things like, "I'm here for an appointment," or, "I have a (time of interview) appointment to see (interviewer)," or, "Is (interviewer) here? I'm (his/her) (time of interview) o'clock." Smiling slightly and phrasing things just a tiny bit away from what someone might normally say can often get people's minds engaged, I find, which actually makes you look good, in most situations.