I find I have two paths to a share:

1) I always ask myself, is this content I find interesting/important enough that I feel it brings value to the people that follow me? If yes, share. A lot of times I'll read something that I personally get value out of but I don't pass it on for a number of reasons...it may be too much of a fluff piece, or the topic is already all over the place, or it may not add something new to a discussion, etc.

2)The second path is usually users who post the fruits of their creative endeavors. Realistically, there is no way I'm going to love the output of most people's music/poetry/writing/video etc enough to share by the same standard I judge most links I find on the web. Here, the important and valuable thing for me is the act of creation, the story you've told that surrounds it, and the feedback you ask for. In a sense, your post is much more than the subject of your post. I generally like to pass these on, especially if I have a connection to the person from knowing them a bit on Hubski. It's the personal element that isn't there on other sites.

So I'm fairly selective with general web content, with a bias towards content creators within the community itself.