I took one class in high school that I really enjoyed. Then I went to a vocational high school and studied Interactive Media Technology, and web design was included in the class.
Also while in the class I had to be a member of Business Professionals of America, which is a giant organization of high school students in programs dealing with the IT & marketing fields. I had to do contests every year, and in my senior year I did the web design one. I got 1st in my region and 1st in the state of Ohio, and I went to the national competition in New York City. I got 5th out of 36 in the nation for the web design competition.
So that's basically how I got into it.
