What education and/or training do you have that relates to your work?
I have a slew of blogs that I read daily, and I also follow Hacker News for technology updates. I tackle new technologies and problems as part of my job every day.
What types of customers have you worked with?
The two most common types of jobs that I encounter are (1) organizations with an idea but who are not sure how to make it a reality and (2) ground-up redesigns of websites or business software involving multiple contractors or consulting firms.
What advice would you give a customer looking to hire a provider in your area of work?
Look for someone with broad experience and several projects under his or her belt. This is not a field that one can pick up from a book or class.
A solid technical background is important, but even more important is exposure to graphic design, information architecture, and usability.