When researching a company there many ways in which you can garner all sorts of information. You can:
1) Read everything the business press (local or national) has been saying about the company by visiting the public library or local chamber of commerce
2) If you really see the need to, you can visit relevant government offices or contact business and trade associations.
3) Ask any of your acquaintances in the industry for information. This would be a good time to tap into any network in your field of interest.
4) If you're a student who is graduating, talk with knowledgeable professors or lecturers who are involved in that organisation's area of activity.
5) Ask the company's neighbours, customers and competitors for information. If you are able to talk to someone who has the time, you can learn much while also expanding your network contacts. Just be diplomatic and careful when doing this because you may be seeing these people again, but under very different circumstances. You don't want to create enemies or burn any potential bridges. Any industry can surprisingly small.
6) Call the prospective employer and request materials that you can collect or have posted on to you before your interview for you to review. Don't do this with companies that are on the small side - they may have nothing to give you, which would be embarrassing for everyone involved.
7) Review the written job description if available. Try to talk to someone who is employed in this type of work or in a related field.
8) If possible, see if you can talk to the person who you may be replacing, but do this only if you're sure this action won't have an effect on your chances.
9) It's always a good idea to talk to other people who work for the potential employer. Once again just ensure that doing so won't have negative consequences. You wouldn't want to be thought of as currying favour.
10) The number one source for finding information about a company is the Internet. However, this source can usually only provide generic and superficial information. To find out what's really going on - and now - will always require talking to people. The Internet should be your first port of call when researching, but never your only source.