I haven't been here long, but my hubscore seems to have risen quite well. I think it's through answering questions in the Questions and Answer sections. Also, raising hubkarma is important to raising the overall hubscore and one good way of doing this is adding links in the hubs your write. When you've finished writing your hub, there will be an option to "suggest link" which highlights certain words or phrases in your hub. Choosing to link these words to the suggested hubs written by other hubbers will raise hubkarma and your hubscore, I believe.