OP: I did not have a 3.75 GPA, but I had a high LSAT score. No strong soft factors, real extracurriculars, double-major, or interesting work experience. Slightly quirky personal statement.
Double majoring will make no difference at all. Maybe if it's something you are really passionate about it could give you something to write about, but so could joining the hacky sack team, if that's what you really love. Law school admissions, for Boalt or anywhere else, are mostly about LSAT and GPA, although Boalt is ever-so-slightly more quirky about admissions for people that they find "interesting." A high enough GPA and LSAT and it won't matter, though. Seriously, though, you're better off cultivating an interesting hobby or leadership position than double-majoring. Find something you like, and you'll be able to write something interesting about it.
I don't know where you are in school, if you haven't chosen your college major yet, but it's probably a little early to be so wedded to any particular law school. Boalt is great, but so are a lot of other schools. If you feel pretty certain that you want to go to law school, keep an eye on your GPA, but otherwise try to have fun and get involved with something you love during college. You'll have plenty of time to figure out which law school is right for you once you are actually applying. Seriously.