Many foreign students choose to do part-time work to help pay their tuition or living expenses. The process you need to do is :

1. You need to obtain permition which is called "Permit to Engage in Activity other than that Permitted by the Status of Residence Previously Granted" from your regional Immigration Bureau.
   You can get the application form at the regional immigration bureau counter or you can consult with your foreign Student Dept. of your school to process application on behalf of you.Generally, most of the school has the system.
   
2. When you obtain "Permit to Engage in Activity other than that Permitted by the Status of Residence Previously Granted", you will be able to work as part time for limited hour in a week.the following table shows you some information of working hour for foreign students:
   

   Full-time students at a university (undergraduate or post graduate) or similar educational institutes as well as students of colleges of technology and special training colleges	Within 28 hours a week (8-hours a day during long school breaks such as summer vacation)
   Research students who mainly audit classes or are auditors	Within 14 hours a week (8-hours a day during long school breaks such as summer vacation)
   Pre-college students	Within 4 hours a day

   
   
3. Then you can engage you in part time jobs. There is a voluntary organisation "Hello Work" in Shinjuku, where they help foreign students to find part time jobs. You can visit their site by clicking the image below. You need to register going to their office.
   
   
4. There are some other Private organisations and websites who introduce to different part time jobs in different categories and places all over japan. I am going to introduce some of them here. If you register to those websites, you can receive emails about part times jobs and can apply to part time jobs online.