Social networking is a great way to promote your content. With each new post or article be sure to share across all your networks. But Facebook, Twitter, etc. aren't a one-way street. Set some time aside from your routine to cultivate your connections. Read posts and like, comment. Follow people with like minded ideas. Be genuinely interested in what they have to say and more often than not they'll return the favor.
Also, always look out for new networks or old ones that you're not a part of yet. Connecting with people doesn't have to be about getting them to read your content. It can be a great way to get new ideas and meet other freelance writers. Keep that in mind the next time your cruising the social networking scene.