Gheorghe,
I just go where my nose leads me. Sometimes, I get wrapped up in a certain sound, and I'll circle around it for a while before moving on to something else. Over time, I'll almost certainly come back to it again later.
Often, while I'm doing focused listening like that, I'm reading books about the topic, whether it's jazz singers or Latin Jazz or whatever. But there's no real "rhyme or reason" to it -- other than my own curiosity.
I've found that sort of focused listening helps me gain a foothold on styles that are less familiar to me. It's a sort of immersion, like learning a new language.
But I also sometimes go on benders for the opposite reason: I'll listen to Ellington for two weeks straight precisely because it is so familiar to me; I already understand his idiom.
My jazz blog projects are just another form of "circling around" on a given topic -- a way of sharing what I already know but also pushing further outward as well.