Here are some points to evaluate your digital agency:
Your company’s goals should be clearly defined.
Consult with the agency to learn what their definition of success is regarding digital marketing.
Review the fees they charge.
Conduct personal interviews with your most viable candidates.
For a sample of their recent work, you should ask for case studies.
You can find their corporate blog on their website to know more about their work.
See what their social networking profiles are like.