Honestly, I wasn't asked any difficult questions. The interviewer didn't go with the generic, "Tell me your biggest weakness" or "Tell me about a failure in your career". Instead, she asked specific questions related to my experience. My recommendation is to have a few examples of positive impact you have had with each position listed on your resume. From what I gathered, they're not looking for clever responses to difficult questions, instead they're looking for people who can clearly demonstrate successes in their career.
