There are several networks to choose from: social networks such as Facebook and Twitter, professional ones such as the popular Linkedin, and those in-between, such as Google+ and InterNations, as well as websites whose visitors might be interested in what you’re offering, or which might be ready to promote your site or exchange links.
Facebook and Twitter seem to overlap somewhat, with the same people using both media, so posting to both might be redundant (although Facebook allows more space for expanding on a post than the 140 character limit of Twitter). Besides widening connections, Linkedin offers the opportunity to join professional groups and to take part in discussions. I haven't decided whether Google+ is worth being connected to (I don't think it's decided itself what it is), while InterNations is a fairly small but interesting network of expatriates. As for other websites, that depends on who and what you're targeting. In my case, I've contacted or am in the process of contacting other writing and writing resource sites, book sites and others.
How much should one reveal about oneself in order to achieve one's goal? That is, if one has a goal. Barring the compulsive networkers, there again that depends on who and what you're targeting. As I proceed along the learning curve of networking, I expose as much as I need to in order to promote The Writer's Drawer. In other words, while I disclose no personal information because it seems irrelevant, I do say that I'm an editor and a writer and expand a little on my professional background. The fact that I've lived in several countries lends a cosmopolitan touch to me and to the site. Sometimes I hone in on someone who sounds interesting and introduce myself. Some answer, some don't. Some might promise to contribute a piece of their work to the site, and a few actually follow through.
I guess networking has helped bring traffic to the site and has put me in touch with some creative people. I have to admit that without networking, the site would be a much less interesting place. For better or for worse, it has also made me a little slicker and a little more thick-skinned as I learn to interact with people online.
I, and possibly other readers, would be curious to hear what you have to say about networking, what sites you use, and how you use them, as well as your experience with sites I didn't mention.