If you have something in common with the interviewer, don't overplay it.
Often people find out they have something in common with the interviewer (i.e, they went to the same school or they know a family friend). Bring it up once. ONCE. Don't keep going on and on about it. Somebody who goes to my university applied for a job with us recently and he continually talked about how cool it was we went to the same university, over and over again. Needless to say, this guy is still looking for work.
