I've got three years left of school before I graduate. I'm planning on teaching English in Japan once I get my degree. While at a used bookstore the other day, I found a book on teaching English abroad and bought it even though it is quite out of date. One of the things the book suggests doing before teaching abroad is to do some volunteer ESL teaching, and I would love to do just that. Are there opportunities for this in Southern California? I'm in Orange County during the weekdays and San Jacinto on the weekends. Even being an assistant ESL teacher would help me greatly. I tried to do a google search for this but the only results I got were for teaching abroad. Any help would be greatly appreciated.

As a volunteer without pay, absolutely there are avenues to teach ESL in Southern California or just about any place else for that matters. Start with the YMCA, local libraries, even a school counselor. Even as a volunteer, they will likely want to do a background check on you, but as long as you have no felony records, you should be good to go.