Don't get too technical. General basic questions very often will determine how much smoke the prospect is blowing.
Aptitude can include manual dexterity, attention to detail, knowledge of electronics and optics, familiarity with AV equipment, "hands on" problem solving, etc.
Specific projection skills are best tested in writing and by "hands on" demonstration and problem solving, similar to tests given apprentices by the IATSE.
------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion
I can guarantee you will never have to worry about it again. 
------------------
Better Projection Pays!
Does your state (or province) require licensed projectionists and force them to be tested for the licensure?
Here in Pennsylvania, the Dept. of Industry is hitting hard on the independents to lincense their operators. I live 3 miles from the border with Ohio so it's not just a greater metropolitain Harrisburg thing if you know what I mean. Any feedback?
To Tim
That would be a relief but I don't think that 25/hr. would jive with my GM.
To Aaron
We can hire anyone off the streets.
Maybe it's a last ditch effort to get money out of people. Wouldn't put it past the state.
A lot of non-profits around here don't use licensed projectionists. We are hiring one part-time licensed projectionist, have an "emergency only" licensed projectionist on hand, and the two of us (Esther and I) will be getting apprentice licenses and go for the Dept of Labor & Industry testing later on.
I'm reading everything I can get my hands on (which mostly comes from this site and the references in the posts) and cleaning every washer, gear, sprocket and undetermined part in the heads that the technition is rebuilding....learning "hands-on" so to speak.
Thank you Brad, for creating this website!!!
I am so impressed with the people who post here!
And thanks again Glenda!