You’re not required to conduct exit interviews, but polling your departing employees can reveal very useful information regarding
their reasons for leaving your company and pursuing opportunities
elsewhere. How do you make exit interviews confidential and effective? Most departing workers won’t look to bash their boss on their way out the door. Even if they were dissatisfied, there is always a sense that the information they provide will somehow be placed in their personnel file and come back to haunt them should they ever look to be rehired by your company. There is also a fear that bashing one’s boss could lead to negative references with prospective employers.

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First of all, you’ve got to decide who will conduct the exit interview.
A member of your organization’s human resources team or a senior
member of departmental management is the best choice. Immediate
supervisors aren’t recommended for this task because their presence
may bias employees’ feedback.

Second, you’ve got to determine whether your exit interviews will be done in writing or via a personal conversation. Ideally, you should do both: Exiting employees coming to drop off their company IDs and to pick up their final checks should be required to fill out an exit interview questionnaire first. Then they can verbally share their experiences with the company during the face-to-face meeting after the written questionnaire is completed.

If you develop a written questionnaire, be sure to construct it so that the information can be fed into the computer and tracked for
trends and patterns. Some of the questions you might include in the
questionnaire fall under the following five categories (which can be
mirrored for staff, as well as for management employees): (1) nature
of the work and job responsibilities, (2) relationship with the supervisor, (3) employee compensation and benefits, (4) career progression opportunities, and (5) reason for leaving. A sample questionnaire covering all five categories can be found in Appendix M.
A brief look at a resigning employee’s responses before the
face-to-face meeting should provide some insightful feedback regarding
that individual’s experiences. The true value in the exit interview
data lies, however, in the pooled information developed
over time and across departments. For example, you can look to exit

interviews to substantiate your suspicion that a particular supervisor
lacks the leadership abilities to motivate and retain staff. Such
objective evidence may help you sell the benefits of management
training to particular supervisors or even substantiate employee
complaints against them in the form of progressive discipline.

One caveat here: Exit interviews work well with employees who are laid off or who resign of their own accord. They’re less useful when given to employees who are being terminated for cause because such employees often lack the objectivity to assess the working situation fairly.

Taken From : The Hiring and Firing Quention and Answer Book