The Rating Scale
My rating scale is fairly straightforward. It's a general analysis of the episode as a whole. This includes elements such as the story's strength, sometimes the episode's validity to the series, and technical concerns (acting, directing, effects). Often, the star rating simply conveys the overall entertainment value of the show. There's no clear-cut application of a rating; it's just a useful estimate of my feelings about an episode.
A great episode — a truly compelling installment.
A step below "excellent," but not by too far.
A good episode. Not necessarily great, but worthwhile.
Okay. It could be better, but it could be a lot worse, too.
Not good ... could be on either side of the line separating "fair" and "pretty bad." Still some grace-saving moments, though.
Ball dropped. Quite bad. We hope not to see many of these.
(or lower) — Abysmal
Like 1 1/2 stars, only worse.