My Super Amazing Awesome Rating Scale:
5 Stars: Masterpiece.
3.5 to 4.5 Stars: Not necessarily a masterpiece, but a damn good show. Represents a great series of the specific genre.
3 Stars: Average show. Nothing that really stuck out, but nothing that made the show a failure either.
1.5 to 2.5 Stars: Show did not meet my standards as a decent anime. Either it was just a show leeching off another show's popularity, or just filled with filler and plot deviation.
1 Star: No, just no. This constitutes a show that completely fails in my eyes, or a show I could not stand to finish.
My scale ranges from from 1 to 5. This means the average show will be rated 3 stars. Half a star is used for anime that falls beneath my standards of a watchable anime.
.5 Star: If a show has been given half a star, it consitutes a show I could not finish (or barely made it through in the case of a 1 episode ova) because it was that bad. I would only recommend these shows as a form of torture.