Hmm I might be in the minority here but I honestly, through my own professional experiences and through those of my friends, don't think that your major will matter all that much.
Don't get me wrong, I think it does matter for certain careers. For instance if you want to be a computer programmer, you'd best take computer science - unless programming is a hobby of yours and you're already much better than your peers AND can prove it on your resume and job interview.
Obviously if you want to be a medical doctor, you should major in medicine (or whatever the prerequisite for medical school is).
If you want to be a professional writer, I'd say something like English or creative writing would be an obvious choice if only because you'll find the subject matter more interesting, and it would be something you'll excel at and enjoy in college. But I don't think it'll help you in terms of actually landing a writing job. I've known so many people with those majors (and art as well) that kind of walk around in a daze after college, honestly not knowing what to do because they hadn't exactly gained any skills.
Landing a professional writing gig is pretty tough, depending on where exactly you are. I'd say it's got a lot more to do with connections than anything else.