5. Domain Knowledge - Does the applicant have any knowledge of your business? This is at least as important as programming skills.
A six month internship is pretty short. An up-front list of projects to attack will be helpful. This could/should include training activities and homework like reading Learning Perl.
My internship(1973) was so much different than today. I came in with Data General assembly language experience which comes with bit level hardware knowledge. "Kids" today learn products.
There's never enough time to do it right, but always enough time to do it over...