The privileges that a process can actually use are in the process's effective set. At the start of a program, the effective set is equal to the permitted set. Afterwards, the effective set is either a subset of or is equal to the permitted set.
A good practice is to reduce the effective set to the set of basic privileges. The basic privilege set, which contains the core privileges, is described in Privilege Categories. Remove completely any privileges that are not needed in the program. Toggle off any basic privileges until that privilege is needed. For example, the file_dac_read privilege, enables all files to be read. A program can have multiple routines for reading files. The program turns off all privileges initially and turns on file_dac_read, for appropriate reading routines. The developer thus ensures that the program cannot exercise the file_dac_read privilege for the wrong reading routines. This practice is called privilege bracketing. Privilege bracketing is demonstrated in Privilege Coding Example.