I've never been to prison, but I read quite a bit about inmate culture and experiences. A few words of advice:

- Don't gamble.

- Don't trust anyone, no matter how friendly they are.

- Don't accept "free" stuff.

- Stand up for yourself, no matter the situation.

- Respect deeply other people, but don't lower your status.

- Mind. your. business. and expect other inmates to do the same.

Sorry if they sound terribly cliché.

We had motto in the Scouts: Estote Parati, "Be prepared". Read the bio and experiences of past inmates. You don't want to look scared and in culture shock mode when you get in. Wolves smell the lack of self-respect.