1) Read what's out there. If you are interested in social media's influence on PR, the blogs are the best place to start. Kevin Dugan's prblog keeps up with new social media and links to tons more resources. Paull Young's Young PR gives great tips for students and young professionals alike. Media Bullseye has several contributors who provide news and commentary about current communications trends in media, marketing and PR. Dr. Russell also compiles a "best of" every week with some interesting links to check out.
Also, check out what your peers have to say. PRSSA members have blogs on tons of different topics. Lizzie Azzolino, Katherine Strate, Ashley Beebe and I all have blogs.
To keep up with the blogosphere, the easiest thing to do is get and RSS reader. Google, Yahoo and AOL all have them.
2) Start slow. Join Twitter, a microblogging site that is sort of like Facebook status meets chat room. It's a great way to share and follow links, connect with people with similar interests, and do some online networking. You might want to read up first so you get the jargon and etiquette before you jump in. (Thanks for the links Dr. Russell!)
3) Go for it! If still feel like you want to be a blogger, do it. Blogger and Wordpress are fairly easy (and free) platforms that will help you design the look of your blog. Once you have a few good posts, put the link on your Facebook profile, Twitter account and anywhere you can find. Plus, if you comment on others' blogs, they will be more likely to check yours out and comment back.
4) Keep trying new things. Post to YouTube. Subscribe to some podcasts. If you are a photographer, try Flickr. If you are looking for a job or internship, join LinkedIn. It's kind of like Facebook, but more professional. (You post your resume instead of your pictures from downtown.) If you're feeling really adventurous, check out Second Life. There are lots of articles about how to use Second Life in the blogosphere, but the best way to learn is to try it.
You don't have to follow all these steps. Some people would rather observe than participate. You will still have the knowledge of social media that many employers are looking for.
Good luck! Maybe I will see you out there in the 'sphere.