Students sometimes have a hard time keeping track of who is doing each job. Use a display board or a space on the chalkboard that outlines which students are taking on each role. This helps the teacher and the students keep track.
For primary students who are still learning to read, consider including pictures with the job title that display the expected behavior. Also using clothes pin clips with student names is a fun way to move the student to a different job and makes it efficient to change the assignments, leaving the pictures and job titles in a stable place.
Classroom Jobs can be assigned whole group. These are usually jobs that are necessary for the classroom to run smoothly on a daily or weekly basis (such as door holder, bathroom monitor, or materials monitor). Get students involved and instill ownership of the classroom by assigning students to take on varying classroom jobs. Classroom Jobs can also be content specific. If you are teaching a specific concept, such as the economy, you can design jobs for students that will teach them a specific skill as well as give them responsibility.