The administrator note at the top of the pages currently encourages us to use our votes on SuperUser because they will be selecting moderators soon. I am not quite sure what this implies (mods chosen based on activity or rep score?), but it got me thinking about how to best choose moderators for the site, and I believe Meta is how to do it.
I think we as a community have already demonstrated an ability to discuss what we believe a site should aim towards (in this case the discussion about defining SuperUser). I do think that had a large hand in why I was asked to be a mod for the site. I believe we could use that same idea for choosing future moderators for SuperUser (and even for other sites as they come through the pipeline).
What I am getting at is this:
Your best moderators are going to be those who are already familiar with how the system functions as well as how the community functions. High performance on Meta is a good indicator of those factors.
We can generally determine who is going to be a good moderator based on how they perform on Meta, since Meta is not only a discussion area for topics about the growth of StackOverflow, but also for helping troubleshoot newer users. Both of these qualities are pretty important for a mod to have.
Reputation scores generally aren't a good indicator of performance on a site other than activity, but at least on Meta, high scores here can generally signify that you are indeed invested in the community enough to engage in all the discussions. Combine that type of enthusiasm for the sites and the community along with a genuine interest in the future of a particular site, and you have all the ingredients necessary to make a good moderator.