You should get regular feedback from the end user (B-to-C with the consumer, or B-to-B with the store manager, technician, anyone using your product).

FORBES: Do You Know Whether Your Customers Are Satisfied?

Clients can bypass the big names and hire consultancies such as Eden McCallum, a British firm that packages teams of experienced independent consultants, or Point B, an American firm that provides only a project manager, letting the client select the team.

ECONOMIST: Consulting bounces back