When beginning research on a particular company, it is a good idea to verify its current name and status. Does it file with the SEC? Is it a subsidiary of another company? Is the company name actually a brand name? Who are its competitors? Directories such as the following can help with such questions.
Tools such as ReferenceUSA and Nexis Uni can be used to create lists of companies that fit certain criteria (industry, location, revenue, number of employees, etc.).
The following tip sheets provide guidance on making company lists: