Generally, when doing market research, consider consulting the following sources:

• Demographic data such as age, income, employment and location
• Consumer and psyhographic information 
• Industry profiles and market research reports
• Articles from trade publications, newspapers, and business magazines
• Industry or trade associations
• Government agencies (e.g., Census, state development agency)
• Press releases from main players and 10-K/Annual Report (if the company is public)

Explore this guide to find quality sources!