An exit interview is a good way of tracking employee perception of the company across a wide number of variables. The HR managers can also find out new ways to improve people management or retaining valuable employees who would otherwise have left the organisation.
The best way to do an exit interview is having a paper based interview because rather than saying their issues face-to-face, they would rather be comfortable writing it and they would also be more honest. Good exit interviews are basically good information about the organisation and it is a good way to assess and improve all the aspects of the working environment, including the culture. Exit interviews basically create a positive atmosphere in the organisation.