One easy way to establish rapport with an individual who is first entering your facility is to utilize the custodial pat search to your advantage. By simply asking a couple of questions you can give the impression that you are concerned about the welfare of the individual and/or his property and possessions.
For example, you may ask someone if they have any money, jewelry or any special item with them so that you can make sure it gets accounted for. Combining this with other aspects of professional communications (i.e., using “sir” or “ma’am”, “please” and “thank you”) can help to create in the individual the feeling that you are concerned and that you are looking out for them.
Whether the person tells you about something you missed during your search, or they feel comfortable enough later to tell you about something going on in the cell block, a few simple words and gestures - which should be part of your professional role anyway - will go a long way to cultivating positive interactions with that inmate.