Talking about work is not the same as doing work. An interview often showcases one set of skills (talking about work) but cannot take the place of observing someone's work. If you want to really know how someone works, give them some work to do during the interview sequence. Are you shocked? Don't be. We recommend this at every level of hire from Executive Director to Administrative Assistant. We explain why we are doing it and I cannot remember the last time anyone took offense. (Remember, the candidates want to see what the work looks like just as much as you want to see their work).
Think about the actual work you expect of the new hire, look for an example of something recent, relevant and somewhat complex. Something that might take 30 minutes, or even an hour or so. Something that tests a critical skill. Something it would be easy to do badly. Then ask them to do it. Perhaps they do it at home and come present it to you, perhaps you leave them alone to do it in the conference room and then come back in 30 minutes.
To be fair and objective about it, you must give exactly the same test to each applicant, at the same phase of the interview sequence (after first interview for example), and with the same set of instructions. For some jobs you may want your instructions to be broad and even vague, for other jobs you may want to be very specific - it depends what you are looking for. It's not that hard to come up with real life work scenarios, but the range of results you get will probably surprise you. That is, of course, why you are doing it. People will make mistakes and judgment calls you cannot even conceive of. Which is probably good to know, before you put them on your payroll.
Rest assured, watching people do actual work will make a big difference in who you hire. Because as I said, talking about work is one skill. Doing work is quite another.
And, if you prefer all that research and information pulled together into one attractive document you can easily share with others, download our Employer Guide to Interviewing.
Of course, interviews are only one component of a great hiring process, our Resource Center has additional topics you might find helpful:
How to Replace Underperforming Employees
How to Write Job Descriptions that Attract Great Candidates
How to Handle Bad Glassdoor Reviews
How to Evaluate the Effectiveness of Your Hiring Process
How to Make Your Hiring Process More Certain, Predictable and Consistent
One disclaimer: This advice will be most relevant to hiring managers who are interviewing professional staff in large metropolitan areas. Our perspective is shaped by our work, and we work in a retained executive search firm, conducting searches for CEO and senior staff positions. We've completed over 600 searches for associations and other nonprofits in major metropolitan areas like Washington DC, New York, and Chicago, so we make no claim that all of our advice will be relevant if you are interviewing for other types of positions in other job markets.