I usually read several reviews on more than one website, both professional and amateur ones, before I make a major purchase like a car, game console or something.  If it's something cheaper like going to see a movie, I might be more easily swayed.  However, when it comes to movies or video games, I always look closely at the review and see if I can guess or notice any bias in the review.  When someone gives a game a really bad review, especially an amateur, I look for clues as to whether or not the reviewer even likes games of the genere that the reviewed game fits into.  Same with movies.  A person who hates "space operas" might give Star Wars a really bad review, for example, while someone who really likes them may give it a high review.