Like with many other causes, you start with yourself -- and that might be enough.
These days, not participating in the latest electronics and social sites and whatnot is enough to make people ask you questions. If you think carefully enough about why you're making the choices you make, then you can give pretty reasonable answers.
I don't own a smart phone, or have a Facebook or LinkedIn account. I still buy paper books. I don't blog (much). And I don't really evangelize these choices; I don't do any of this for attention or to try to change other people's minds. But, when someone notices their tech guy is carrying an old-school flip phone, they ask questions.
Usually the first thing I say is, "they're really convenient, really good tools," immediately followed by, "but, I've noticed that people seem to have a lot of trouble ignoring them, and I don't need another distraction in my life. I don't really want an internet connection to follow me everywhere."
As far as I know, I haven't made anyone else give up their smart phone or Facebook account or whatever. But a surprising number of people take a moment to think about that. They often kinda look at their phone and go, "...huh, I wonder what that would be like..."
And, y'know, just the fact that I get by and live pretty well without these things I think speaks more about how valuable they really are than any sermon I could think of.