If it is a private company, run a search in PrivCo, a database that specializes in providing private company information. Enter the company name in the search box.
If it is a public company, use Mergent Online, Passport, Business Source Premier or Bloomberg Professional Service. Use the search tips in the box: Company research databases and website (found on this page).
NOTE: Most public companies provide access to their annual reports from the Investor Relations section of their corporate website.