Think like an expert
Stick to actual, real, objective questions with concrete answers that a working professional or expert in this field might encounter as a part of their actual, real, job. Stock the site with a bunch of on-topic, expert questions and answers, so that when the site opens to the public, it’s already pre-populated with a bunch of the kind of content that will attract other experts.
You get the site you build
The first questions set the tone and topic of a site for a long time. Those early questions say a lot about what your community could become. And questions asked during the private beta will be on the front page when potential experts see your site for the first time. So please make those first questions exemplary ones that are interesting, challenging, and worthy of imitation.