You should do like I told Cpt S. to do it, and do it how he was originally going to do it. Look through applicants and pick the people you think deserve it.
Have post and Rep requirements though.
I'll post what I said in his thread here.
Edit: Page 4 of his thread.
This:
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The Random.Org thing is fair, but it's also unfair. Also dangerous. What if Random chooses a lecher or someone who doesn't deserve premium.