Ask for a resident to show you their ACGME printout where cases are broken down by category....and, just talking to the residents and senior students.
It's not easy, because so many residents are full of crap, which we all seem to agree on.
I guess the best thing to have is a good bulls@#t meter. If the student is a good judge of character, and can pick up on body language and inflection well, that's probably better than any list of numbers.
Just want to point out that if you get a resident to print out their acgme log that:
1. you need to remember that the year of the resident makes a difference and you can't base the number and balance on this. A current PGY3 is not going to have 1000 cases since they are only halfway through training, and many programs are top-heavy (which may mean 75% of cases are in the last 2-3 years, as a subjective guess).
2. remember also that depending on which part of the log is printed, especially for PGY1and 2s, some things are not shown in the numbers (i.e. central lines and minor procedures, critical care cases, etc.). While most people want all the 'big stuff', doing a lot of the 'little stuff' early on in residency is also a very good thing.
3. it doesn't tell you how much a junior resident is in the OR (watching/participating with more senior residents who are actually taking credit). If my service wasn't busy, any junior resident was welcome to scrub in on a cool case like an esophagectomy, big retroperitoneal sarcoma whack, etc....they'd get to do some stuff, learn some technique but couldn't take credit...sometimes they had to leave and come back if a really long case. I had an intern who would do this all the time and by the end of the year had developed mad skills despite not logging a ton of cases on paper.
4. Always ask about seniors taking juniors through cases. If attendings let chiefs take younger residents through cases, it is a good sign of a. chiefs having sufficient knowledge and experience to do so and b. some resident autonomy. For example, I took juniors through a bizillion lap choles, hernias as well as some trauma GSWs, bowel resections, open choles, colon resections....But you can't see this in the 'numbers', you have to ask. [you can log stuff as a TA, but only up to 50 cases count...many don't even think to log them]
My advice with case log volume is to not quibble over numbers around the average (say 900-1200 or so, depending on program type). Worry more about the programs with barely enough (< 800) or a ton (> 13-1400) of PRIMARY cases. These are places where you really have to ask questions like "how much do you get to do vs how much are you just bovie-ing between the attending's clamp", "how do you count whether to log a case?", etc. As others have said, you don't want to be somewhere that you may not get enough cases, but you also don't want to go somewhere that counts any case regardless of how much you get to do.