You ask a good question Ashley. Many of us would like to know the answer to this question.
If there is a formula it seems only a select few discover it. I can say that even those with Hub scores of 100 seem to easily lose them. Some never gain them back while others do.
Evidently, and I could be incorrect, the main goal you need is to have your author hub score over 75. That allows your links to be do follow and worth more to the search engine visits.
There is a hub by DonnaWallace that purports to explain how to increase the personal hub score.
How to Increase Your Personal Hub Score (aka Hubber Score)