Part of the answer to this question is obvious. Never ask questions that are prohibited by the EEOC, so that means never ask questions about age, race, sex, religion, national origin, ethnicity, health, or sexual orientation. Why? Because none of these protected categories have a thing to do with the ability of a candidate to do the job or perform the required tasks. The ADA has also limited the reasons an employer can deny employment to a candidate with a disability, even if the disability requires the employer to make a “reasonable accommodation” to make it possible for a candidate with a disability to do a particular job.
So, what’s the poor employer to do in order to find the best people for the job? Is there any point, furthermore, in even bothering to talk to references? Yes, of course, there is. All that’s required is to make sure the questions asked are strictly limited to job performance and nothing else. It’s perfectly fine, in other words, to ask about things like previous job responsibilities, ability to work with others, personality on the job, strengths and weaknesses (as they relate to actual job performance), management style, career development needs, eligibility for rehire, and reason for leaving, etc., etc. As long as the questions relate to job performance and nothing more, it’s perfectly fine to ask.
Another topic many employers think they can ask about is what people do on their own time. What people do when they’re not at work is none of the employer’s business and should never be asked. On the other hand, if the prospective employer, or its agents, wants to ask something like, “Is there anything else you think I should know that could adversely affect the candidate’s ability to do the job for the prospective employer?” that’s perfectly fine. Why? Because the question relates specifically to the candidate’s job performance! If the response is something like, “Well, so-and-so may be late to work on Monday’s pretty often because he spends every Sunday getting drunk,” that could affect the employer’s hiring decision because, once again, the behavior cited impacts the ability of the candidate to do the job!
The best rule to follow is to ask questions that directly relate to job performance only. After all, assessing the ability of the candidate to do the job is really all the prospective employer needs to know in order to make the best hiring decision possible.