Doctorow, is a convincing advocate. I read his books, feel fired up that I can make the world a better place, and then the real world rumbles over me.
But I once read a writing tip from Cory, that even if you write for only twenty minutes a day, in a year you will have sizeable number of words.
I guess the same applies here. Lots of small actions regularly, will make a difference. Signing e-petitions, for example takes almost no effort. Most don't work, but some do, and its start.