First off, a human Hub Team member only "officially" reads your hub for two reasons:
1) if you're new to Hubpages and a hub you write during your "honeymoon" period is noticed and gets nominated as a Hub Nugget, or
2) Your hub is flagged for review by other hubbers because it violates HP policy (pornographic content, for instance, or overly commercial) or the content is substandard (poor grammar, excessive spelling errors, or it's plain gibberish, to name a few).
The score for any hub you write is determined by software that employs a mystical mathematical formula called an algorithm which uses many factors to come up with a score at any given time. Among them are number of words, keywords used, the types and number of capsules used (i.e. a hub with multiple text and photos capsules plus a video and a map or a poll scores higher than one that contains only one text capsule and no photos. Also, traffic and comments from within and outside of HP affect the score. The more traffic, the higher the HP score and the higher your rank on Google. Hubs that include summaries rank higher than those without one. The length of time a hub has been "up" is yet another factor. "Ever green" hubs that will generate traffic year round score higher.
Your personal hubber score (the number you see in your profile pic) is, again, determined by the algorithm and based partly on how many hubs you've published and partly on how much you interact within the HP community. This includes reading and rating the hubs of others, leaving comments on hubs you read, being active in the forums (Hubber's Hangout, for instance) and in "Answer".
The score on any individual hub will always fluctuate up and down. That's just the nature of the beast. Editing a hub whose score has dropped into the 60s may or may not bring it back up. Adding non-text or non-photo capsules may or may not help. There's no particular writing style that guarantees a high score, other than it be free of grammar and spelling errors so that it doesn't get flagged for "low quality". People like what people like. Hubs I thought would be duds were hits.
The best advice I can offer is keep writing PLUS visit the hubs of "Hot Hubbers" and study what gets their hubs high scores.