Use a Review-Sniffing Site
If all of this sounds like a lot of work, there are some existing tools that you can use to spot fake Amazon reviews. They may not be a perfect replacement for careful vigilance, but they could do in a pinch.
Services like ReviewMeta and FakeSpot will analyze product reviews and spot any signs of inauthenticity. Both platforms use slightly different means of analysis, so it can be handy to use both to determine whether a product is worth buying.