You have obtained an interview – congratulations! You feel prepared to discuss your strengths, your accomplishments, your willingness to work hard and learn quickly, and your ability to fit seamlessly into the employer's needs. But … you do not know anything about the employer. You may not even be sure what kind of industry they are in. Do some quick homework before your interview and you may glean a basic understanding of their business that can set you apart from other candidates.
In the "old days" you would have needed to visit a library to try to find the employer in a Manufacturers' Guide. Now you can use the Internet to investigate. If you are lucky, and find that they have their own website, explore it completely, like a search engine spider, page by page and link by link. It will provide you with genuine insight into their organization, their accomplishments, and their values. Try to identify what kind of problems and challenges they may be facing which you could address in an interview. If the company does not have a website, Google them and see if they show up on another site.
If you know their product or service (if you do not, anonymously call the receptionist and just ask what the company does) search for their name within similar sites. If you can not find the company anywhere, or can not find any helpful details, look at the industry they are in and see what is currently a hot topic and what predictions for future change are being discussed.
All such information will be immensely valuable in your interview either to demonstrate your ability to solve problems or, at the very least, allow you to ask intelligent, pertinent questions.