The only way to truly become proficient in GIS is to simply use it. The coursework will only serve to provide a base knowledge of the field and without some form of practical experience, most companies will not be interested in hiring. To find internships check with your school's geography or urban planning department. Oftentimes companies and agencies looking for student help will advertise there. You can also directly inquire with places that you are interested in working for.
Internships can lead to full-time positions.
There are quite a few job sites on the internet specializing exclusively in GIS employment opportunities. So write up a resume and cover letter and hit the internet. Aim for jobs that meet your education and experience level. Digitizer - little to no experience needed. This is the entry level position in the field.