Define the industry you are researching and keep in mind that many industries are made up of smaller, private companies. Some companies operate within more than one industry. In addition to using some of the databases below, remember to try to identify trade associations, government agencies and other relevant experts, groups and publications.
U..S. Census Bureau Data
Remember that everyone would like to know who buys how much of what, why they buy it, when and where they buy it, etc. Start broadly and drill down.