If they are looking for a job, if they have a face full of metal, (nose rings, etc) you 'll not work for me. They can have piercings and "be cool" off your site, at work, it's a hazard, and potential customer scare factor.
Two, if they're looking for a job, do they look like an electrician, or potential to be?
Have them draw out a 3 way, and four way switch set.
Ask them simple electrical questions, amperage questions (like how many amps allowed on #12, #14),to see if they have electrical knowledge. How high of the floor to a receptacle, or switch? What size is a "typical" breaker for a service, branch, circuit,dryer,etc.
Put a "We drug test" sign in the window. It leaves it as an option, but not mandatory, and hopefully discourages the ne'er do wells.
Ask if their serious, why they're leaving where there at, and it will also tell you about how they may leave you (if you hire them).
Ask if they've ever heard of Mike Holt.