To be honest it is really difficult to say, but I will try my best. There are two scores - the HUB score and the HUBBER score. Both fluctuate and all the veterans on HubPages say that this is normal. I have made a few observations. I have noticed that when I have more external traffic my scores are higher.
Take advantage of social networks and build your external traffic. Use sites like Facebook, Yahoo Answers, Twitter and others to promote your links/hubs.
The most improvement I saw was when I began building my Blog with links to my hubs. Create little summaries of what your hub is about and add a link. Promote the Blog on Twitter and Facebook. (NEVER directly copy any part of your hub other than the title onto any other site) My Blog is OlivePedia.com if you would like to see how I link to my hubs.
Create quality hubs and be informative on your topic. Add graphics. polls and videos when possible. The hubs you write represent you. Think quality over quantity.
As you start building your hubs you can start grouping them and linking them together. This helps you promote your work in niches of interest.
I hope this helps! Hubs you might want to consider reading are - Hub Boosters, Referral Trackers and Blogs - Grab that Traffic - Yahoo! Answers, Seek, and Ye Shall Find. All of these hubs were created with the purpose of promoting traffic.
Continued best wishes and feel free to ask if you would like further help. :)