This kind of good writing is made, not born; you have to work at it, practicing continually. Classes that require written assignments and projects are a perfect opportunity to sharpen these skills; avoiding them is a cowardly mistake.
Instead of watching the TV news, read the newspaper; instead of entertainment TV, read an entertaining novel.
Someone who doesn't read is hardly better off than someone who can't read.
You should use your undergraduate years as an opportunity to learn about the world, about the achievements and diversity of humanity. After you graduate, you will find yourself concentrating more on your career and your family, but while you're here at UCI, it couldn't be easier: Just sign up for a course, be it botany, Russian drama, art history, or Chinese politics.
One of UCI's greatest strengths is its diversity; take advantage of it, and good luck!