This question is actual for me. On week ago I've launched community for programmers which have a new approach to organizing content. It allows users share their posts using tags. And as you noticed - there is minimum content for now. So on this early stage people don't understand why my site can be useful for them. Another problem isthat I am not native speaker, so probably my explanations can be unclear. Anyway I am working on several articles about the idea of my site and will submit it on HN, Reddit. Also I am trying to write posts, submit links, add code snippets on the site. At least - in this case the site looks like alive and not empty.

So, I can say that everything depends on the community niche, main idea of the site and what problems of users it can solve. You must have a good understanding of people who can be interested in your site and have a set of ideas how you can motivate them to start using your community. Anyway on the early stage you should at least make the site look alive.