There really isn't an "interview" process, you'll sit down and talk with a recruiter and they'll ask you questions about what you're interested in and what your goals are. They'll check to make sure that there isn't anything legally or medically that would stop you from getting accepted. If they really care, they'll make sure that the job you go into is a good fit not just for you, but for your family as well (if applicable.)
For a job as a Cryptologic Linguist I needed to pass the ASVAB Test with high scores (I got 97/100) and score 110 or higher on the Defense Language Aptitude Battery (I scored 118/176, anything above 110 qualified you for a top-tier language program at DLI Presidio of Monterey as of 2010.)