Consistency is the best policy in evaluating applicants during the interview process so all candidates are measured against the same job-related criteria.
An employer should avoid personal questions or anything that might be construed as discriminatory when interviewing job candidates. The focus should be on exploring the applicant's ability to perform various job tasks.
There are special concerns to take into account under the Americans with Disabilities Act when interviewing a candidate with an obvious disability, or one who requests an accommodation during a job interview.
Emerging technologies, such as video, have added new considerations to the interview process.