We go out and look in the garden. . . sometimes we find them sleeping under the cabbage leaves.
No, not really. 
People ask for applications. We send them one. They either run screaming in horror when they see what we ask of them or they fill out the application and return it to me.
I send the application to Ed and he looks at it as needed. Input is solicited from the staff as to anything noteworthy about the candidate. The application is at some point processed and a decision is made.
Ed takes a lot of time scrutinizing what people say in the application and he spends even longer looking at their postings on the board. Some of you have thousands of posts and he has read all of them.
Candidates are evaluated for fitness – how well they would do in the sometimes adverse conditions that happen around moderators. How would they handle the stress that comes with the position? What do they do under severe provocation? What kind of work habits do they have in terms of holding up their end, reading forum areas, policing the joint? How will they work with the existing Straight Dope staff – we really need to pull together as a team and much of what we decide arrives by consensus.
We often go a long period of time without adding or subtracting from the staff – we’ve had times that we had no changes for years. Then again we’ve had times that due to various circumstances we needed to bring other people on board. It’s not predictable because people’s lives are sometimes wildly unpredictable and what worked great yesterday does not suit today.
We recently had a couple of moderators retire. We brought two more people on board to replace them. The process continues.
Mostly people approach us first, though sometimes we see someone who is such a sterling potential candidate in their everyday board life that we approach them. Some of our best moderators were so fabulous as posters that we wanted to see more and they gave us more.
We are very grateful to everyone who hears the call to serve – the overwhelming majority of applications note that they have gotten so much out of the site and the greater Straight Dope community that they feel a need to give back. That means there’s something awfully right going on here that people feel so personally invested in this place.
The time it takes to process a moderator application varies due to time and circumstances and the need for staffers. The shortest time an application was considered was 10 minutes – and that guy got hired. He did a great job for many years and is now retired. The longest time an application sat before judgment was, I believe, several years. We brought that person on staff as well. Everyone else was handled in somewhere between those two time periods.
Generally if we have a full complement on staff we collect applications but don’t completely process them – there’s not an urgent need and the day is full with other stuff, always.
Not everyone is appropriate as a moderator. There are people who have applied that had the very best of intentions but honestly they would be terrible moderators. It’s not a vote on someone’s popularity or an evaluation on their fitness as a community member or a human being, though some have taken it as such. Some have judgment issues. Some have issues of temperament. Not everyone works well in an collegial environment. Others are not be able to put in the time and do the work we ask of them. But we appreciate everyone who wants to help. Sometimes the very best thing you can do to help out is to be a great community member, it’s not a situation for everyone, not at all. “Many are called . . . few are chosen.”