well.. I really concur with a comment that Cheeks made.. that you should not feel obliged to select a major simply to prepare for law school. You're still very young and since you're contemplating a law education, you really should undertake a discipline that you are genuinely interested in. You never know.. your goals may shift.
LSAC recommends taking challenging courses that help to build your reasoning, writing, and critical thinking skills.
It says that you could build on these attributes by taking courses in the social sciences, natural sciences, philosophy... quite broad in fact
Of course that doesn't mean that you should blindly pick a demanding curriculum - unless you really want to and you feel that your interest in the subject will allow you to do reasonably well.
I'm completing my business degree and only recently decided to go into law. Even so, my major has really helped to define the area of law that I would be interested in. I'm really glad that I took a bunch of electives in economics, philosophy, and liberal arts earlier though cause it helped to balance things out.
I guess my advice very much echoes what has been expressed by the two that posted before me.. that is, to study what interests you (and make this judgment in the context of your strengths)
Just be sure to work hard and maintain a competitive gpa (this is especially important if you want to study in Canada). I wish you well!