Originally Posted by AcronymAllergy
Speaking with students in each of the programs, as roubs suggested, is also a good way to get a feel for how things go. Many grad students are honest about how happy they are with the program; if they love or hate it, they'll usually tell you as much.
This is definitely true--during my PhD interviews this past cycle, it became very obvious that the students at some programs (most of them, thankfully) were very happy and that the students at some programs were, uh, not. Students will also frequently give you hints or inform you outright as to whether or not their mentors are easy to work with.