A highly-effective way of preparing for an interview is to put yourself in the interviewer/employer's shoes before the interview. If you can anticipate what they want to hear you will have gone a long way in winning the job.  

To begin with all employers want to hear that you can do the job! This may sound obvious but many people walk out of interviews failing to convince the employer that they can deliver even though they have all the experience and knowledge to do so. Not only do you have to convince the employer that you can do the job but you also have to convince him/her that you can do it better than the other candidates! Here are some great tips that work well:  

Talk less about your skills and more about your achievements. As much as possible quantify your achievements in measurable outcomes. Say, for example, "As a result of my actions our customer service satisfaction levels increased by 15% or product defects fell by 10%". If you don't have specific amounts offer a best guess. Make sure you can back up your best guess - in other words don't just pull a number out of the air.

Wax lyrical about key achievements that are meaningful to employers. What is meaningful to employers? Try these for size:

-Productivity levels

-Efficiency/process improvements

-Consistently good customer service

-Attention to quality in terms of service and product

-An ability for their company to respond to changes quickly  

If you were diligent you would have done your homework before the interview. One of the things you would have been keen on finding out would be the problems or areas of improvement relating to the job you're going for. Your worth in the eyes of the employer will skyrocket if you can utter words to the effect: "My research indicated that one area where your processes can be improved is xyz. That's an area that I can really help you with because I can do abc." Be very careful not to inadvertently put down the employer's operations when saying this.  

Employers also want to hear that you're a highly motivated individual who will be able to fit in with the existing culture. An effective way of doing this is by:  

Doing your research on the company (this demonstrates high levels of motivation as well as preparedness).

Mention what it is about the job that motivates and excites you, e.g., duties, skills and knowledge required, environment, expected outcomes etc...

Make a point of highlighting why you think you will be able to fit in with their environment. If, for example, you're expected to be a team player, make sure you can demonstrate, by example, what a great team player you are.

On the other side of the coin there are some things that employers definitely do not want to hear. Avoid these like the plague:  

Being negative about yourself! Again this may sound obvious, but you would be surprised how many people insist on "opening up" and bearing their souls at interviews. Leave the soul bearing to when you're in the company of friends. Interviews are about selling yourself by highlighting what makes you terrific.

Avoid criticizing former employers and/or managers. You may have legitimate gripes but criticizing former employers does not make a good impression on potential employers.

Do not dwell on all the problems you faced in your former job. Instead, mention them briefly and then focus on what you did to fix those problems. Don't forget to mention the outcomes in measurable terms.

Do not just talk about your skills and knowledge. By all means mention them but the successful candidate will demonstrate how these skills and knowledge will specifically add value to the organisation.