It is essential for you to know something about the company before you go to the interview.
One option is to simply check out each company's home page on the Web. Companies of all sizes and in all industries are constantly popping up on the Web. Since most sites are geared toward consumers, most individual company Web sites include detailed information regarding the company's products and services. Others might include a company history; a list of company officers; and financial information.
In addition to finding company Web pages, you may often find that companies are listed in two or more Internet databases. And, you probably will want to search several databases for each company you are researching. If you find the company you are looking for on a datebase you may be tempted to simply disregard the additional information and move on to a company you do not have information about. However, it is wise to compare the information contained in the different databases. If the information is consistent, then it is probably safe to assume that it is correct; if the two sources conflict, you should try to find a third source to determine which information is correct. It is also likely that many databases will contain different information; one may have financial information, and another may have a list of chief executives.
You should also take care to watch the timeliness of the information you are finding; while most online databases are updated frequently, that is not always the case.
For more information,
the following is a great tutorial for researching companies online.