Look at that: Matt Dahl, a 3L from my alma mater (University of Richmond School of Law) who is "not an expert in national security law but wants to work in the field" started a blog on the subject.
This is really smart. When I was at UofR, I joined a couple ABA committees - I was often the only student on the committee, and it was a phenomenal way to meet people practicing in the areas of law I was interested in. (Ironically, one of the lawyers I met while in law school was Stewart Baker, then the GC for the National Security Agency.)
Starting a blog on a subject you're interested in is a terrific way to gain a fluency in the issues that matter, identify who the leaders in the field are, and attract attention as someone willing to learn more on the subject. (Who knows - you might even find you have a unique insight to offer, which will immediately stand out to those in the area who are looking for new thinking on a particular subject.) On those ABA committees I was pretty often the note-taker. But that forced me to understand what I was taking notes about, and meant I was usually the one e-mailing the follow-up notes to the attendees of the meetings I was at.