How to judge a potential graduate student based on a short interview? In my department, we typically have many more applications for MS/PhD students than we have open positions, so it is a &quot;buyer's market&quot; from the professor's point of view. Each student submits a relatively standard application package of grades, a resume, any awards or trophies from various academic contests, papers or patents they've published, and recommendation letters. Based on this, a short list of students are invited for short (&lt;20 minutes) face-to-face interviews either in person or via teleconference.
My typical questions include:

what kind of career do you see for yourself after graduation?
what about my research interests you most?
explain your particular contribution to your undergrad research project

My problem is that many students look superficially the same, and in the interviews it is difficult to move them beyond standard responses that they know I want to hear. My belief is that this is my fault because I am not asking the right questions. While most of the students I have eventually accepted ended up working out just fine in my group, my error rate is still well above 0%, both in terms of gems I let go and those who were admitted but didn't excel.
In my perfect world I would be able to probe just that one level deeper to separate the wheat from the chaff. Are there any good tips for how, in a 10-20 minute interview, to get a deeper sense of a student beyond their &quot;on paper&quot; appearance?
When interviewing candidates for industry jobs, I concentrated on two issues:

Is the resume accurate, or if inflated how much? A resume is a sales document, and candidates do try to present themselves as favorably as possible, but it should be fundamentally truthful.

Can the candidate discuss technical issues in the relevant field?


Everything else is covered by the paperwork.
Fortunately, there is one form of question that can help resolve both issues. Pick a topic, such a research project they claim to have done or a course they did well on, and ask about it. Do they know as much about the topic as the resume indicates, and can they discuss it?
As Buffy suggests in a comment, zero error rate may not be possible. Ultimately, you just have to do your best and accept you will make mistakes.