The admin probably watches over everything and evaluates the quality of how one posts. Users who follow the rules, don't bully, ect... would make the best possible mod. That's how I would do it If I was an admin.
Your best bet would to PM RMJL who is the forum admin and has the final say forum wise, I would write why you think you would make a good mod. Also know she will go through your post history with a fine toothed comb! You don't have to be prefect though, I even have one infraction from back in the day!
This. Touching illadelphin inappropriately is a sure way to become a mod. How do you think we all got where we are today? Really though, if you want to send in a mod application, PM RMJL. It's true that only members who are very trustworthy end up on the mod team, for obvious reasons. But you're always welcome to send a PM and get your name out there as a potential moderator.