Technically I've been on Twitter since 2008 or 2009, but I only started really using it this summer.
I have avoided social networking (and the Internet in general) as a rule, because it makes me crazy and I have had problems with it in the past (thanks, IRC).
However, following agents and writers on Twitter has proven valuable, as I've gotten tons of links and found out about all kinds of things I wouldn't have otherwise.
I have had to curate my list carefully, though. I started out following everyone that seemed interesting, and then, making sure to READ everything that everyone posted!
That was not sustainable, and I've adopted a far more reasonable approach now: check once or twice a day, scroll a bit but don't try to catch up on an entire day's worth of tweets, and, most importantly, I've culled my Following list to only those who I truly want to follow.
It's been working a lot better for me. I don't feel like such a slave anymore.
Only four more days of 2014 left!