How to build your resume over winter break?

I’m a current college freshman, and my winter break just started. What can I do to improve my resume? I was thinking perhaps job shadowing, but I’m not sure if I can put that on a resume. I would just be able to add those people on LinkedIn. Any suggestions?

Take your resume to the career center and have them review it.
Look for summer opportunities, if you don’t already know what you’re doing.
Work on learning a programming language or some other skill that is relevant to your field.