For my department (each one has a different process), I searched for a new GSI position each semester - and for 3 out of 4 semesters, I taught outside my department ... simply because there weren't enough jobs to go around. Departments would post GSI positions, often through email listservs, and students would respond to the department administration. Again, each department is different ... but I don't recall interviewing with the professor I'd be working with, only the admin (HR) person.

To begin the application process, you should apply online and submit your resume. Afterward, arrange an interview with the professor to thoroughly discuss your qualifications and explore the specific needs and expectations of the role. This will also provide an opportunity to understand how your skills and experiences align with the job's requirements.