If it looks like they've created an account just to write a review, it could be fake. Another obvious sign of a false reviewer is the same short review for a wide range of products. Check if the reviewer's purchase has been verified. Some online retailers will tell you.
A review that shows that it comes from a verified purchaser is more reliable than a review of an alleged purchase that hasn't been verified. While there are many customers who use and review the products for free immediately after their release date, this is far from normal. In exchange for a free product, a consumer can be expected to use certain phrases when reviewing the product. About eight out of ten consumers believe that they may have read a fake review last year, and the same number indicates that they aren't sure if they know how to spot a fake review.
However, on some websites, you'll see a label or badge next to the review that indicates that the author received an incentive.