To Tweet or Not To Tweet?

We all know that social media, and the internet in general, is a huge time suck. BUT, it is also a great way for  a new author from a small press to get her name out to a lot of people. I enjoy blogging and my facebook page because I think they make me feel real and accessible. I love that. I want people to be able to tell me what they think, start conversations, etc. Goodreads is super awesome. It's a whole website dedicated to books. How could it not be? Yet I know as my book's release date gets closer I'll need to do more, so I'm asking: What do you recommend? Twitter? Tumblr? Something else? What is the best way to connect and still have time to actually write?