Good staff are almost always chosen from within the forum membership, 'chosen' being the important word. Never ask for volunteers, just pick from the best of the active members and make them an offer
... but don't pick someone just because they are very active; it's a good trait in a moderator because you want someone who enjoys being at your site a lot, but some of the most active members can also make for zealous moderators if promoted (not because they are horrible people, but because they are just sooooo passionate about the site!). You need someone with a cool head (so they can take a balanced approach to problems) along with the strength to tackle issues regardless of who is posting or causing difficulty (your best posters/longest serving/most generous members shouldn't get special treatment or be subject to less or no moderation just because of who they are!). Also don't make the mistake of bringing too many moderators on board if you don't need them; demoting moderators can make them feel quite upset and offended - no one likes being thrown off "the team"! Promote as needed (and I mean really needed) and select level-headed, polite, clear communicators where possible. Cheers, Shaun
I used to put up applications years ago but I found it lead to a lot of resentment and jealousy amongst members where one was given the position and the other wasn't. These days I invite them to become one based on a number of factors and so far I haven't had any issues doing it like this.