Your university or education institution may have a careers service or job board you can use. Ask your student advisor where you can find help in finding and applying for jobs. And be sure to check if your university or university union is hiring. There are often lots of job opportunities on campus.
Check out the ‘Careers’ or ‘Employment’ page of the websites of business that often have part-time or casual jobs available, such as:
Even if the company you want to work for isn’t advertising right now, you might impress them by sending your resume anyway (but be sure to include a cover letter introducing who you are and why they should hire you).