use research to discover, evaluate, and refine
Formative research is the first stage, designed to get you out there and understand the space and industry. Spend time with your users to understand the terminology, the standards, and the gotchas of the products.
Evaluative research is testing the assumptions on your product. Talk to 3 sets of 5 users to discover 80% of the problems of your product. Make sure you're talking to your market, not just family and friends. Iterate in between.