It is beneficial to establish beforehand a number of facts pertaining to the company on which you have been granted an interview. If is it a publicly-listed company, most probably you can obtain a significant degree of information from the company website and company directories. In contrast, private companies are allowed a great deal more confidentiality, hence information about private companies are pretty hard to find.
Company website serves as a valuable information source for information pertaining to corporate missions, values, culture, products and services and directions.