Chances are good that you conduct exit interviews with each employee who resigns. We’ve all heard how valuable the data from them can be. But chances are also good that you’re not doing much with that data. Here’s some advice from an expert on how you can make good use of all those findings.

Who interviews departing workers? We asked Beth N. Carvin, president and CEO of Nobscot Corporation, who should conduct exit interviews. A long-time HR person, Carvin remembered being assigned to interview someone who’d worked in marketing in a financial services company.

She was aware of problems in the marketing department and tried to probe for the former employee’s views—tried every way she knew to get him to open up. But he was determined to say nothing beyond that he was leaving for a better opportunity; he consistently stonewalled her. Determined to get a better handle on the process, Carvin began spending concentrated time on the problem.

First, she says, never assign the employee’s former supervisor to conduct the interview. One of the most important things organizations should be able to assess through the process is how effective individual managers are. (Remember the oft-repeated saying that employees don’t leave companies; they leave managers?)

Then, the more distance you can put between interviewer and interviewee, the more accurate and honest the data you’re likely to glean. Have HR do the interview, and make it by phone to add some distance. Better still? Hire a neutral third party to interview. Best of all? Automate the whole process, so that interviewees enter their answers on a computer.

How do you collect the data? First, Carvin advises, sit down with some colleagues and review your interview questions. Ensure that you ask the same questions, in the same order, of every interviewee; if you ask a couple of questions and then let the interview go where it may, you won’t get reliable data. Create a mixture of questions that will yield quantitative data (e.g., “On a scale of 1 to 5, how would you rate x function or y aspect of the company”?) and qualitative findings (“Please describe your relationship with your manager.”).

Next, plan to collect enough interview data for a long enough period (depending on the size of your organization and the number of departing employees, it could be 2 years or more) that you’ll have enough to make it worth aggregating. Carvin advises smaller companies that can’t afford to automate the function to use third parties for interviews and aggregate the results on a simple spreadsheet.