1. Spend some time doing some background research on the client and client context so that you're prepared to address the client as a well-informed, professional researcher.
2. Request an interview in advance. Explain why you want the interview, how long it will take, and what you hope to accomplish. Be professional with this request and formal with all subsequent interaction so that the client knows you are conducting research and not just "chatting."
3. Although a live interview may work best, you can also consider interviewing the client by Skype if it is more convenient for him or her.
4. Come to the interveiw prepared with a list of written questions. It’s usually a good idea to give clients some questions in advance so that they can be prepared as well
5. If you wish to record the interview (audio and/or video), you must ask permission first.
6. Take notes during the interview, even if you use a recorder. Your notes will help refresh your memory when you don't have tune to review the entire recording; they can also help you identify the most important points of discussion. Because give-and-take is important, it's often a good idea to have two people on the interviewing team present; one to take notes, one to conduct the interview.
7. Be flexible. Don't try to make the person you are interviewing answer all your prepared questions if he or she doesn't find some of them appropriate or interesting. If your interviewee shows more interest in a question than you had anticipated or wants to discuss a related issue, just accept this change in plans and return to your list of questions when appropriate.
8. Try a variety of questioning techniques. People are sometimes unable or unwilling to answer direct questions. So try rephrasing questions. Be more general or specific, depending upon what you think your client will respond to well.
9. If you transcribe the interview and use it for any other purpose, you must give the client the option to review a transcript and the option to revise where necessary. Under no circumstances should you publish (to the Web or elsewhere) an interview with the client without the client’s consent. (In journalist interviews, that permission is normally granted implicitly; good journalists, though, will often take the time to confirm quotations.)

Expanded and adapted from from Lisa Ede’s Work in Progress, 4^th Edition. New York: St. Martin's Press, 1998.