When interviewing applicants, apply the same standard that is applied to job applications - ask only about things that are directly related to the job requirements for the position under consideration.
Watch out for tape-recording - the applicant might be tape-recording the interview without an employer's knowledge, and a video- or tape-recording of an interview would be discoverable in a discrimination claim or lawsuit.
Tell the managers who conduct interviews to be extremely careful about note-taking during interviews - anything like that can be discovered in a claim or lawsuit - many discrimination cases have been lost due to careless and/or embarrassing comments written by interviewers.
Test for whether something should be written down: would you feel comfortable explaining it in front of a judge and jury?
"Working interviews" are not the same as pre-hire interviews at which an interviewee might demonstrate how he or she would carry out a sample task - an "interview" during which the worker performs actual work and receives what most companies would call "on the job" training or orientation to the company is work time - a company must pay at least minimum wage for such training time, satisfy all of the usual new-hire paperwork requirements (W-4, I-9, new hire report, and so on), and report the wages to TWC and IRS.