How to succeed at interviews for research positions

Given that we work in a research institute, it is often our job to take on trainees, pre-PhD candidates, post-doctoral researchers and even fellow faculty applicants.
I will focus currently only on the amusing incidents (that also highlight a potential lacuna in the preparedness of interview candidates), in order to make the process more productive for both the candidate and the interviewer.
Despite the long-term nature of PhDs and the effort and cost involved in preparing (entrance tests, travel, hard studying, etc.), it always amazes me how poorly prepared the large majority of PhD candidates are when they come to interviews.
My top-3 list of amusing answers that are symptomatic of this:

1. Q: Why are you applying for a PhD programme?
   A: Ummmm……. I haven’t really thought about it.
2. Q: What was the most exciting research you have read about in the newspapers, magazines, journals or anywhere in the last 10 years?
   A: I don’t have time to read, since I am busy preparing to crack competitive exams.
   OR
   A: I have read about protein X (put the last thing they mugged before boarding the train/bus/flight), and how it affects Y (disease) by Z (mechanism).
3. Q: How will you make a 1 Molar solution of any reagent?
   A:I will hand the bottle to the technician.
   OR
   We were not taught this.
   OR
   It’s the fault of our College/Professor/University, that I can’t answer that question.

Interestingly, most interviews focus on how well the candidates basics are. Having said that the perfect candidate is the one who has mastered the basics- the degree certificate is validated- AND has original ideas about what s/he wants to do in future.