This requires you to be familiar with the terminology and jargon used in the population. Unstructured or semi-structured interviews allow you to explore various issues in depth with respondents. If you start getting into life history, you're probably doing depth interviewing, which is something completely different. It is all right, however, for you, the interviewer to talk about how you would answer a question, as long as this is to clarify the purpose of the question or set up an instructional pattern. Self-disclosure should be avoided if it seems like it's leading to interviewer bias.
Interviews are wonderful opportunities to impress the importance of confidentiality on respondents.
A somewhat important issue with interviewing is time of day . Some people are diurnal and others are nocturnal, which means they talk more during the day or at night. Many criminal justice populations are nocturnal, so you get the best information at night. However, safety issues must be kept in mind. Interviewers should not be overdressed nor underdressed.