6- Work for your university
There are hundreds of part-time jobs on campus for students, including bar work, events work, admin jobs, and giving guided tours to prospective students.
With decent pay and hours (as well as usually being quite close to your dorm room and your lecture theatres), these jobs are gold dust.
It also helps that the university already knows you, so are likely to be able to provide a glowing reference when you look for work after uni. Our advice would be to apply early, as these jobs tend to disappear quickly.