Call or visit your library to get the information you need. JobStar's Libraries section will get you started. In addition to information on public companies, Hoover's includes information on 2,000 private companies. Search by company name, location, industry or sales. Forbes 500 Largest Private Companies Annual December feature from Forbes ranks the 500 largest private companies by revenues.
Free information includes a link to company website.
If the newspaper permits you to search past articles, look for any coverage on your target company.