I use http://10secondguides.com/ every game until lately. Lately I find myself making more personal choices but when I was learning it was really helpful to see what items are for each lane and what options you have.
I usually look at guides for champs I've never played and don't really know how their kit works in the first place (I had no clue what any of Trundle's spells besides the pillar did until yesterday). I try to look at guides just to see what other people are building so I can try those builds out and see if I like them better than what I normally build.
Generation 30: The first time you see this, copy it into your own signature (on any forum) and add one to the generation number. Social experiment.
I don't look at guides that often. I do still look at them for most champs though, every now and again because you never know what insight you might find. I don't read them in as much detail any more though.
I usually look at a couple to get a feel for what items/skills are maxed in what order, especially if I'm a bit rusty with said champ. Then I pick and choose what I agree with.
For example, I liked Oddone's suggestion to get a Giants Belt after Spirit Stone but before Elder Lizard for Hecso I tried that out. I didn't agree with buying Visage last (especially since I was against double AP), so I didn't follow that advice.
"Whats the penalty for dodging in ranked?" "Phreak comes to your house and punches your screen."