My suggestion is to combining the token system with your classroom helper routines. the tokens system relies on classroom jobs to reward children, rather than rewards contrived by the teacher. Whether of not you chose that method, here are some ideas for making your classroom helper set up run efficiently and effectively:

-Assign all routine jobs to specific students.
It would be very distracting to have to pull a token to determine (or randomly choose) who will turn the lights out each time you leave the room, or who would collect papers, or worse, always do those tasks by yourself. You want instruction to be uninterrupted- any regular classroom task which you want to be performed automatically without your attention should be assigned. Use tokens for privileges such as calling students to line up, selecting read-alouds, carrying things, doing bulletin board displays, and other tasks which do not have to be done automatically to keep the classroom flowing.

-Have students keep jobs for a month.
That way you remember who has which job (in case it isn’t done, or the student is absent), and the child can get good at it. Switching jobs daily or even weekly can lead to confusion and poorly done tasks, because the children forget what their jobs are and how to do them properly.

-Allow children to choose their jobs so that you know they will be done well.
Most of my kids don’t want to refill the soap and paper towels in the bathroom, and if I assign that job to them, they won’t do it to the best of their ability. However, there are always a few kids in the room who love this task, and if I allow them to volunteer for it, I can be sure it will be done routinely and to my standards. I have my children choose in order of how well they did the previous month’s job (those who did not need constant reminders and did their jobs without asking picked first- we discussed this as a class so they would understand my criteria and reasoning), or according to social skills grades (i.e. the most responsible students who followed class rules picked first). Both ways made sense to the children, but you could pick randomly if you prefer. Students can pick a job they have already had, but not two months in a row (they will naturally keep track of this mentally so you won’t have to remember it). If there are no jobs left that a student wants, s/he can opt not to have a job and someone else can take two (this has only happened once, but it gives the kids a sense of control and empowerment).

-Have students train one another to do classroom jobs.
The last two days of each month are our training days. The last person to have the job teaches the next person how to complete the task. That means I explain how to do each job only once- to one child per job in August. After that, they teach one another. If they have a question, they are to ask the person who had the job before them. Occasionally I give reminders, but the ‘turnover’ each month is generally very smooth.

-Discuss expectations and hold kids to them- don’t be afraid to ‘fire’ students who don’t do their jobs!
We talk about how adults can lose their jobs if they are not on time and if they do not do their jobs well. Starting with the second week, any students who still are not remembering to do their jobs or are doing them sloppily are given 'verbal warnings' and 'additional training'. I have the child select someone in the class who they think could be more responsible, and the two of them do the job together for a day. If the child still does not meet expectations, the child they selected to help them is given the job for the remainder of the month. This may not be appropriate for all classrooms, but if my students cannot remember to take the attendance down after two weeks and with a buddy to train and help them, I think it is fair to hand the task over so that the classroom can run more smoothly. It's never done as a punishment, only in the interest of completing mundane tasks quickly and accurately so instruction can be the priority.

-Assign a Star of the Week for when you are too busy to pull tokens (or choose students) and when you are out of the classroom.
Sometimes at recess or in the hall or at an assembly, a child needs to be chosen for a small task, such as taking a note to another teacher or retrieving something from the classroom. Your Star of the Week, or VIP, or whatever name you choose, can serve in this role. There may also be an unassigned task that pops up during a lesson, and rather than distract the class with tokens, just ask the Star to do it. This seems fair to children and they do not question it. Each child usually gets to be Star twice a year, and gets to hold his or her regular monthly job during the Star week. I like assigning the Star job for a week so that I can remember who it is, which would be hard if it changed daily. The Star can also share favorite books and poems, bring in an item from home (like a show-and-tell), eat lunch with you, or any other special activity that draws attention to that child and builds self-esteem. They can also be the substitute for monthly assigned jobs for any students who are absent.

Examples of Assigned Monthly Jobs
These are just a few ideas. I usually add and delete jobs over the months as classroom needs change. I like to have one job for each child in the class, partially so no one feels left out, but mostly because I always have at least 25 or more routine classroom tasks that I need help with! Some jobs can use 2 or 3 people.