I usually don't look at the star rating and just read the comments and pay attention at the language they're using. Another thing I do is look at the website the developer has listed.
I remember getting Darkroom and at the time it was getting very poor ratings because people didn't read the description about the in-app purchase required for the level settings. You see that across a lot of the free apps with IAP, so I don't take the star ratings seriously because of that.
Another thing is that people tend to take stars off just because an app doesn't have a feature. And yeah, people do rate stuff badly simply because they don't understand them too, instead of just letting it go and deleting it/asking for a refund.