If you are take some art classes, get a base for art and visual communication - graphic design. Read/buy books on posters and graphic design. I personally like to buy books and build my own library.
Get a firm grasp on sketching. In today's "computer age" too many people are getting away from using the pen and paper. Computer and software should be the tool for final design work...getting those sketches into a final look.
Speaking of computers. Graphic design uses a lot of memory, so get one with at least 512MB of memory or higher. I recommend an Apple Powerbook. Most designers use Adobe's Illustrator or In Design. Photoshop is great also. I also use CorelDraw, more than I use Illustrator. One more item, get a drawing tablet, it's a piece of computer hardware that lets you virtually "draw" on the screen. The tablet can wait until you've mastered the design software first and is not a MUST HAVE right away.
As far as College: Columbus College Of Art & Design is one of the best as are others too many to mention here.
Good Luck
"I've had two years to grow claws, Mother, and they're Jungle Red!" Mary Haines - The Women