As a high school junior, I already knew I wanted to be a writer. When I looked at small, liberal arts schools (small was just about my only criterion at that point) I found many with creative writing majors. I realized, though, that what I needed first and foremost was a grounding in literature -- the British and American traditions that I hoped to bask in and borrow from.
At W&L I studied under great writers, got to meet Pulitzer-winning poets when they came to campus, acted in a few wonderful plays (big surprise: you learn a lot about writing by living in a story for six weeks of rehearsal). But every bit as important were my studies of Chaucer and Ovid, Pynchon and Morrison. There are many ways to be a writer, but there's no substitute, I believe, for deep study of the best literature available, the best stuff produced in hundreds of years of human effort. You'd be surprised how many aspiring authors (despite expensive Master of Fine Arts degrees) have only read their contemporaries. I've always felt that I got my MFA the same day I got my BA: a thousand literary heroes, well-taught and well-studied.