If I'm not sure what Stack Exchange site to ask a question on, what's the recommended protocol? Do I ask the meta-question here on meta.stackoverflow.com? It looks like there are several "Where should I ask..." questions here, and the FAQ doesn't really cover this area.
Asking here is fine. As I mentioned in my comment, either somebody will be able to give you a definitive answer, or at least will point you to a site-specific meta if it's hard to tell 100% if your question would belong on that site. You can then get further clarification there if needed.
We even have a tag dedicated to this entire concept; tag your question here with site-rec!
I'd start by browsing the directory:
There's a fairly succinct definition of each site there.
While there are some grey areas of overlap between sites (the example I always use is URL rewriting questions, which could be on SO, SF, or even Webmasters), it's not too difficult to resolve by asking yourself "what's my job title" or "what professional hat do I usually wear?" and ask it of that community.
In other words, if you have a question about motorcycles, you don't start yelling out your question on crowded street corners hoping someone will answer. You go to the place where motorcyclists hang out, first...