I do rate some animes up a little, and my ratings are based more on enjoyment then anything else, but the plots and storyline also effect it. So if I enjoyed it but the plot could've been better it'll get a slight lower rating, etc.
0.5 - never recommend, avoid it
1 - not going to say to avoid it but probably would never think of watching it again, it's just bad.
1.5 - lost interest, I got overly bored.
2 - Meh, it wasn't great or awful but still was boring and/or generic.
2.5 - It was alright, not too bad not too great but just alright. A middle ground.
3 - It was simply okay, not bad!
3.5 - Good :)) it was fun to watch, I might think about watching it again.
4 - Amazingg, interesting, had me interested in every ep! I might watch it again!
4.5- Sheeeeesh it was great, fantastic even, something I'll definitely remember and probably rewatch.
5 - YES. SO GOOD. 99.9% CHANCE I'LL REWATCH IT. Definitely worth buying!!