> I ask all the interns that I interview to hire, "why do you want this job?" I can pretty much tell by the answer alone whether or not they are going to work out. Those that say, "I didn't know what to study" or "I heard there was a good career in this" I can pretty much write off.
I would be careful about making that assumption - it was only 4 1/2 years ago when I landed my first job as a developer after 2 1/2 years of searching for any career track job after leaving my PhD program in mathematics. I was someone who was willing to do anything and was open to a wide variety of jobs. I put in long hours outside of work early in my career to learn and grow, with the mindset that I was behind and needed to accelerate my learning greatly - I had a work ethic that might be seldom seen in the industry, and a proven intelligence to match.
Fast forward to today, I am right now actively interviewing and being hotly contested by many companies for senior, lead, and management roles, including the likes of Google and Apple with multiple onsites scheduled or being scheduled (4 alone between Google and Apple over the next week or so).
IMO companies should try to tease out characteristics of people - how do they handle difficult situations, how open are they to feedback, how hard are they willing to work (especially earlier on), and how smart are they? Positive answers to these questions when interviewing inexperienced people are probably the biggest factors in determining the likelihood of someone being successful IMO (don't ask these questions directly of course, but the answers should be teased out).