If you are switching jobs:
The replacement of job shouldn't be an excuse for labelling the workplace you have worked in as poor. You should show your boss why you are leaving the business and you ought to point out things that bothered you, do it in a polite and professional method however. Keep a measure of professionalism that has led you to this point in your career. This assists you to make strong references in the future. In conversations with fresh potential employers, it's important to be professional.
It's also advisable to tell your superior you are grateful for the chance that you have had in working for his or even hers business. You never know when your present boss will end up being a great reference. Be aware that no one likes to become criticized. Not from subordinates or colleagues even. Should they deserve it still. Anyone with whom you possess ever worked with can be a potentially positive reference. Usually do not demolish the bridges behind you. Maintain genuine contacts.