There are many "silent rules" when it comes to prison. This is the first thing you need to realize: If you find yourself in such an unfortunate spot of heading to the "big house," make sure you learn the etiquette and rules of engagement before entering the facility.
Once in there, take some time to JUST OBSERVE. Do not talk to anyone about much and just sit and watch. Keep to yourself as much as possible. Some may introduce themselves, but keep yourself kind of an enigma at first and just sit and watch...read a book, draw, do whatever that requires just you to sit on your own and take it in. Sit in the pod and see who seems to be in charge and call the shots. Be sure no one has laid a claim on chair or table first before you sit there. See the flow of how things go in the area, like phone use, getting food, using the microwave if there even is one, when to take showers, bathroom use, what everyone seems to be doing and with whom, and just watch human behavior and take it all in. Watch how people line up to leave the pod and if there is a pecking order or if it just first-come, first-served.
Often times there are phone lists of when prisoners "merge" calls certain times of the day. The lists are sometimes written around the phone or carved into the wall, or whatever and not always obvious and you will get confronted if you overstep on someone's time and can get "phone checked," which could mean just the phone being forcefully hanged up or you even being hit with the phone, and even full-on fighting. Merging is when one prisoner connects on 3-way calling with someone else, usually another prisoner. A family member or friend facilitates the call.
Look to see who is coupled up or in a relationship and who hangs out with whom. You do not want to find yourself being accused of acting too friendly with someone's significant other. In any group of humans, remember, we are animals and exhibit animal behavior. Take it all in and learn. You were given by God two ears, two eye, and ONE MOUTH. Use your eyes and ears and your mouth less.
Observe, take it in, observe and learn the "silent rules" first.