I usually try to find the most detailed reviews, which isn't automatic but does help. Someone who can speak at length about using the product probably has useful information. I also tend to ignore the star count until after having read their comments.
There are also some tools that try to strip out the most obvious fakes and give you an adjusted rating. No promises for their utility, but I've used reviewmeta.com with success.
Biting the hand that feeds IT
