Hmm... That's a tough one... In running my server, i have found that the best method of picking moderators is to observe them over a long period of time (say a few months). If you observe that the player has good problem solving skills, seems to be responsible, respectable, and have self control, (and that they haven't been bugging you to be a mod), I would then propose to them that i want to make them a mod. The issue with "applications" Is that anyone can say that they're perfect on an application, and over the short term act perfect. But you really need to get to know someone before you give them such power as to be a moderator.