I only flip through the mags to read the paragraphs about sleepers. I like to get a sense of what the "experts" think about various unknown guys to get an idea of who I might shoot for in the late rounds. Very occasionally, you'll find something in there that is worth a damn, but 95% of the research I do is online, and I would go with the info I get at the cafe and the experience I get doing offseason mocks WAY before I trusted some magazine.
NOW, one good tip is this:
Buy a mag now. Flip through it when you're bored, and then take it with you to draft day. Inevitably some shmo shows up to the draft and has forgotten his/her mag and/or hasn't taken the time to do much research. It's always good to have a 4 month old mag laying around to loan them.