If I weren't writing, I'd be teaching and doing amateur theatricals in my spare time. I would probably be teaching drama in a university, but high school would also have been enjoyable.
My most important advice to up-and-coming writers is to establish your own relationship with your literary forebears. Take no English or American literature classes, and if you can't avoid them, then don't believe a thing they tell you about what's good and bad in literature. Read everything and form your own opinions. It's perfectly all right to despise any "great" writer and love any "substandard" writer for whatever reasons you have. You aren't STUDYING literature, you're MAKING literature, and the critics and teachers are utterly irrelevant to your task. To the degree you believe them, you are destroying your own future work. But the storytellers of the past, THEM you must deal with, learn from, and rebel against.
But in avoiding literature classes, don't let yourself be chased out of grammar classes. Even if to you grammar is exactly as fascinating as doing scales and exercises on the piano, remember that you can no more become a writer without command of the rules of English, in every detail, than you could become a carpenter without acquiring and mastering the use of hammers, saws, and planes. Not that you think about grammar as you write -- instead you know grammar so well that it flows naturally out of you. And when you break the rules, as I often do, you break them knowingly, and not just because you have no idea what you're doing.