It's pretty simple, really. I look at the game he's reviewing, I take an educated guess if he's interested in the game or just baiting fans, and then I see what his criticisms of the game are. If they're things I don't really consider criticisms (I don't like RPGs it's a bunch of inventory faffing and dialogue, I don't like RTS it's all about commanding units) then I see whether he says anything nice about the game like 'it's pretty, it has a good plot, it's easy to get into' and then I weigh that up with what else I've heard about a game and make a decision.
It's such a functional system I use it on EVERY reviewer and review. It'll never catch on though.