Aside from achieving top grades, I think I'd try to play the military card. I am sure that there are former JAG/line officers in the judicial ranks. That could be a hook..
Yeah, don't place too much stock on your "military card" - you need great grades (at least top 25%) OR the right connections as well. The clerkship application process is really a crapshoot - you never know just what might catch a Judge's eye. For that reason, I always erred on the side of including extracurriculars as long as they weren't controversial.
To better your chances of getting a clerkship:
When you go to law school, figure out which teachers know the judges (you can usually do this by figuring out which ones are heavily involved in the state's judicial college or whether they clerked for a judge). Take a few of their classes, do well in them, and get to know those teachers well. An extremely solid recommendation (or even a phone call) from a teacher who knows the judge on a first-name basis can often secure you a clerkship.