An informational interview is a meeting or phone call initiated by you. It involves contacting people in fields of interest to you and gathering information about those fields that could help you make valuable decisions. You will be conducting the interview, however, it should be a low pressure situation for you allowing you to make a good impression.
Since you are interviewing for information only, use this opportunity to learn as much as you can about particular occupation. You may want to ask, modify, or add to the suggested checklist of questions here.
Prior experience and lifestyle
Supply and demand
Referral to others
Be prepared that the person whom you are interviewing will probably want to know something about you as well as share information about her/himself. S/he may even tell you of job openings or inquire as to whether or not you are interested in hearing of any. How you answer will depend on where you are in your job search.
You may or may not be ready to commit yourself to a particular occupational field. In any case, try to keep options open for yourself and respond accordingly. Answer questions regarding your skills and background honestly, and with a positive attitude.