The only things that affect your hubscore are not gaining traffic to your hubs, not communicating enough on hubpages, not being active here, pretty much any form of inactivity causes your hubscore to go down rapidly. The direct opposite will occur for being highly active, and this is what I've experienced thus far in my short 4 months on here.
The number one indicator to me though other than all those things is when you fully publish your hub, this is when the numbers game gets kind of topsy turby.
I've shot from a 97 hub score at the start of the day, and at the end I was at 93, after fully publishing 5 hubs in a single day. So just realize that your playing with an algorithm here, that is averaging out every bit of digitized inputs and outputs that your profile is responsible for generating, including search engine ratings and or statistics. So no unpublished hubs have a zero factor