Ask HN: How to find and assess QA/test people?

As a developer, I know I can find other developers on websites like Hacker News, Stack Overflow, GitHub, etc. And I know I can assess other developers by looking at code samples and by having them write code to actual problems in an interview.

However, when it comes to recruiting someone to work as a test engineer, I am totally stumped. I've read a few things online but I still don't know where to start.

  - Where can I find QA people? Do I just advertise on a regular website?
  - How do I assess their skills? Do I have them write test cases for a real program?
  - What sort of skills should they possess coming? Do they need domain knowledge?

Thanks for any help you can give me.