From the departing employee's perspective, an employee exit interview is a chance to give some constructive feedback, and to leave on a positive note, with good relations and mutual respect. It is better not to blame and badmouth your boss and colleagues even if you have genuine reasons to do so. Be calm, fair, objective and as helpful as possible. In the future you may wish to return to the organization and you may cross the paths of your ex-colleagues, managers in the future. The exit interview is an opportunity to shake hands and leave friends, not enemies.
Here is a list of probable exit interview questions: