If it looks to me as if the person writes the kind of stuff I like to read, I'll follow that person. I may not be able to read everything the person writes, but it gives me an idea of where to look when I have time to read. I also read the Hubs of people I don't generally follow, so that cuts into time for reading too. Mostly, I look for "general writing", rather than one person who writes about all the same stuff. I never want to read product/sales Hubs at all. I never read SEO-overloaded stuff with a bunch of links. Something else I won't read is stuff that looks like the person struggles with English grammar. Another kind of Hubber is the one who posts as his user picture a photo of a model or actress with the idea that doing that will get more traffic. I like all kinds of different subjects, though; so that leaves a whole lot of people I might like to follow.
Basically, I look for "real writing" (complete with substance, decent grammar, paragraphs, etc.), as opposed to quickie-looking "blurbs" with links that suggest more substantial information can be found there (when, really, there's no substance "there" either).