for santa clara correctional officer,
1) know who the boss is for the department
2) know a little bit about the department, they will ask random stuff. Size of department and how many officers roughly i believe.
3) they will ask about your phs.
such as job termination. public fights, your general sense of your behavior, getting kicked out of school etc.

second source of information from a friend when he met with his BI. each bi probably has their own set of questions to ask.