If questioned, indicate clearly that you are not seeking a job from them but merely conducting career research which will help you make better decisions. If the present time is too busy for the person you contact, ask when would be a better time in the future. Be sure and ask for directions and parking information. Do not exceed your requested time, but be prepared to stay longer in case the contact indicates a willingness to talk longer. Dress as if it were an actual job interview.
First impressions are always important.
Take the initiative in conducting the interview. The interview is in your ball park. You ask the questions, you interview the person. Ask open-ended questions which promote a discussion and cannot be answered with one word responses. Once inside the organization, look around.