It will benefit you to learn as much as you can about the industry in which your product or service is represented, and about any companies that make or have made your product or provided your service, or a related product/service. You may also need to access country information. For example, if the resources needed to make your product, or the labor force that will produce your product, exist outside of the U.S., you will need information about the relevant countries.
Look up companies to find financial data, competitors, and reports on company activities.
Look at an investment research report for your company or a company that produces or sells similar products to see what you can learn about the industry or company.
Looking for data for a private company?
Unlike public companies, private companies aren't required to disclose financials and other info--so it can be difficult to find detailed information on private companies. It's even more difficult if it's a small private company.
Beware: It is difficult to find high quality information on private companies. Even though the sources listed here are "better than average quality," sales figures and other private company info are often wrong even in these sources.
Companies traded on U.S. stock exchanges must file various reports with the Securities and Exchange Commission (SEC). The SEC makes these reports available via EDGAR. This includes the 10-K, 10-Q, 8-K, proxy, registration, and other forms (but often not the Annual Report to Shareholders).