If you are planning to study visual or performing arts in college, you have many options. You need to first consider your past experience and training in your intended major.
This depends on what the specific college requires. Some will want portraits, stills, graphic, and/or authentic (organic) work.
Most are very selective. However, just like with colleges, some more so than others.
Generally, a small panel of faculty members from the appropriate department will view your audition. You are expected to be well prepared. If there is a script or musical piece, it is nice to have copies of those available for the panel.
There are many elective courses that non-majors can take. Review your college catalogue and speak with your advisor about your options.
Research the specific audition requirements for those colleges on your list that have auditions. Pay close attention to deadlines and locations of the auditions. Practice a lot and record your work.