The U.S. government takes working illegally very seriously. This page will help you learn the basics of the work authorization process.
There are limited work opportunities available in the United States for F-1 students. For this reason, before coming to the United States, F-1 students must prove they have the financial ability (e.g., present bank statements) to pay for tuition and living expenses while studying. If you decide that you want to work, the first step is always to talk with your designated school official (DSO).
If your DSO knows you are working without permission, they must report it through SEVIS and your record can be terminated. That means that you will have to leave the United States immediately, and you may not be allowed to return.
Below are the 4 main types of opportunities to work in the United States depending on your visa and program of study.

On-Campus

On-campus employment is work that F-1 students whose status is Active in SEVIS status may apply for. On-campus employment is specific to work that takes place on campus or at an off-campus location that is affiliated with the school. Examples on on-campus employment include working at a university bookstore or cafeteria.

Off-Campus

Off-campus employment is work that that takes place outside of a school campus. Off-campus employment is only available to F-1 students who have completed at least one full academic year of their program of study, and who have an economic hardship that qualifies for the Department of Homeland Security’s emergent circumstances.

Curricular Practical Training

Curricular Practical Training (CPT) is an alternative study, internship or other type of required practicum that is offered by a sponsoring employer through your college or university. CPT is only available for F-1 students when it is part of an established curriculum within a school. CPT must relate to your program of study, however, unlike OPT and other work, CPT can be full time and is not restricted by a weekly 20-hour work limit.

Optional Practical Training

Optional Practical Training (OPT) is a form of temporary employment that directly relates to your program of study. You can apply for OPT during your program of study, which is known an pre-completion OPT, or after you finish your program of study, known as post-completion OPT. In order to apply for OPT, F-1 students must request approval from their DSO. A DSO makes this recommendation by endorsing a student’s Form I-20. Then the student must file the Form I-765 with USCIS, if approved, USCIS will issue a Form I-766. You cannot begin to work until you receive your Employment Authorization Document from USCIS.