Depending on what type of artist you want to be will determine what track you follow as an artist.
What do you like? What medium do you like to work in? What inspires you? What art field have you seen that excites you? Whatever the answers are to these personal questions might help you decide what track to pursue as you work your way to college.
The simplest answer though is just do it. Just draw, paint, design... Just do it now and keep doing it every day and then when you're in college do it some more. You become the artist you want to be by just doing what you're passionate about.
Once you hone your skills, learn, practice, understand and continue to improve you'll begin to find your place and the career that works for you.
Check out the website in the suggested steps section, it is a nice list of art and art related jobs.
Eric recommends the following next steps: