Starting questions: Under what names is this company known? Who owns them? Is it private or public?
Since private companies are not required to file reports with the SEC, inforamtion is not always available on these companies.
One strategy is to see what a company will provide you directly. Some private companies do produce annual reports and sometimes post them on company websites. Keep in mind that there are no regulations or guidelines on this information. It is provided for promotional reasons as a courtesy by the company.
Another strategy is simply to look up articles about the company. Sometimes these will include financial information and more general information that can help you evaluate a company.
The following resources can help you find what information is available:
Some major types of reports filed with the SEC:
These reports and more can be found using the following tools: