Usually it's something that you volunteer for after you've been around for a while, or when you've accustomed yourself to write comments on the applications thread while not being a recruiter.
If you want to be recruiter you can write your critiques there, and if they're reasonable, a recruiter will simply have to validate them and barely have any effort. Eventually it'll make a lot more sense for you to volunteer as recruiter and be promptly assigned the job.
It's a simple way of assuring you have recruiters whose opinion match the org's mindset and standards.
Note: When I say "you" I mean pretty much any member
Noteynote: Being able to judge any kind of replay is also something important and something that you can practice by writing those app reviews without being a recruiter
Last edited by Oblivion; Dec 28, 2012 at 03:56 PM.