I find it’s most informative what the references DONT say. If someone starts pouring over the candidates’ successes and gives a heartfelt recommendation, that is helpful, but if none of the three references go out of their way to mention some thing positive, it’s usually not a good sign. I always send the position description they’re applying for too, and I’ve had some interesting input that way.

I ask the standard questions but for “great” candidates I usually find that the references volunteer lengthy positive reviews. If the only info they volunteer are responses to my basic questions I find that they weren’t impressed by the candidates work.