When an interviewer asks a candidate about his or her last job and why the candidate left it, a good answer demonstrates that no bridges have been burned with the former employer and that the candidate was simply looking for the next step in his or her career.
1. Don't badmouth a former boss.
This is among the worst ways to answer the interview question "why did you leave your last job?" The way the applicant answers questions during the interview gives the hiring manager some of his first glimpses of what that person is like. Badmouthing a former boss makes the applicant appear unprofessional at best and difficult to work with at worst.
2. Don't provide a long laundry list of issues.
The interview is not the place to rant about one's former boss or any other aspect of his last job, and it's definitely not the place to perform a long monologue about all the complaints one has ever had with his last employer. Even if the applicant words his complaints professionally and tactfully, choosing to list many little details may be a red flag for the interviewer that the candidate is unfocused, capricious and may leave a job because of the slightest dissatisfaction.
3. Don't give a vague answer.
While the candidate shouldn't provide too many details, providing too few can hurt his or her chances as well. Simply saying "it was time for me to move on" or a phrase to that effect may make it appear that the candidate is hiding something, such as leaving on bad terms or being fired.
4. Don't say anything that reflects negatively on your work ethic.
It's well known advice for job seekers that they shouldn't ask about vacation time or sick days during the interview. Similarly, they shouldn't cite these as reasons for why they left their last job. In both cases, it reflects poorly on the applicants' work ethic if it appears that these benefits matter more to them than other aspects of their careers, such as making a productive contribution to the company with which they are employed.
--Published courtesy of Brafton