This is rapidly becoming a hot issue across the entire network: how to promote your site and how to reach out to the experts and pundits in your industry. We can come up with budgets and promotions but — more than any other issue raised here — the means and ideas about how to reach your target audience HAS TO come from you and your community. Has to. Has to, has to, has to! We simply are not experts in your field. We don’t have the the connections nor the experience you bring to the table. You are both our evangelist and our ambassador.
What this site has to offer right now, compared to other audio production q&a sites, is a pretty uniformly civil and helpful tone.. StackExchange sites are not "forums", and they don't have the ego-puffery/self-promotion and clubbiness that is such a part of the character of, for example, GearSlutz.
On the other hand, the level of sophistication of the audio discussion here is still quite low. There are a lot of smart people on GearSlutz, and you can pretty much guarantee that somebody on that site will know the real answer to almost any audio, production, or gear question. Here, not so much, yet.
There's a bootstrapping process of getting knowledgeable answerers involved by having other knowledgable answerers already there, which will raise the level of questions that get asked and answered. At a certain point, you start showing up in Google results for common questions, and that's a self-reinforcing cycle that leads to successful sites like Stack Overflow (that's how I got involved with Stack Exchange sites).
Right now, this site needs to attract more people who aren't necessarily experts but have practical experience with music and recording, are pretty good writers, and don't mind helping newbies.
A few more experts wouldn't hurt, though... Back In The Day (tm) it just took a few folks of the caliber of Mike Rivers, Scott Dorsey, and Bob Katz to make rec.audio.pro an amazing resource for anyone who wanted to learn about recording and production.
One of the best ways is going to visit other sites like FutureProducers.com and MPC-Forums.com and GearSlutz.com and tell them about the site when it goes live. A lot of people are afraid to ask questions but in a SA site, they're much more active (or so it seems). Getting to these sites and finding the mavens of those sites and have them come over to help might be a benefit.
As the only stat we are really behind on over at Area51 is the Questions Per Day number, I think we need to not only promote by sharing the URL with individuals in the industry, at Music & Film colleges and on forums, but we also need to keep posting questions ourselves. As they say, traffic generates traffic.
I know - I'm a terrible example, having only posted one question, but I will try and come up with more useful questions, and I would encourage everyone else to come up with more. We have 1500 users, so if even a quarter of us posted another 2 questions that would make a significant difference.
This would require involvement from the StackExchange folks, but how about advertising on online magazines like http://mixonline.com/?