So obviously there are different kinds of art, and different kinds of art markets. One of the things that I learned at the Massachusetts College of Art and Design was that if you have a portfolio of hyper-realistic work, you were targeting certain clients, such as game or movie character design. If you have a portfolio of heavy blacks and action packed scenes you are looking at comics. Child-like themes and colors might get you into children's books - if you know the right author/publisher.
Still, one of the markets most often overlooked by young illustrators is the editorial market. By some paradox, it is currently one of the biggest markets for Illustrators to pursue, and a market in which fame is a true potential. Think of J.C. Leyendecker with his Saturday Evening Post covers, or Norman Rockwell before him. For a more contemporary example, Fred Harper Illustrates "The Week" covers.
While these three artists have fairly realistic styles (Harper sometimes borders on caricature), other editorial markets idolize a focus on line and shape and composition. Using only a few key elements in an article, an artist can convey the contents of said article in a single image, grabbing the attention of the reader.
While the image below may not be the most exciting or fun thing that I've ever created, I will say that I feel it is technically strong, and it is the first of what I hope will be a series of images that will help me break into the editorial illustration market. This image is self promotional, but it is based on this Spirituality & Health article: