Some people might not agree, but I only rate dramas I fully completed. I never rate dramas I dropped.  Everyone likes different things for different reasons. We all have our personal preferences and tastes. Even after reading reviews, the best thing is to find out for yourself if a certain drama is your cup of tea or not. In the end, the rating is just a number. Watch what you want regardless of others' opinions. :)

9 to 10- Memorable drama. Story, writing, acting, characters, and OST, are all fantastic. Also, my personal level of enjoyment while watching is something that can't be put into words. That feeling you have when something makes you think differently about yourself or others, or your outlook on life. A drama that is hard to move on from and you find yourself re-watching or going back to your favorite parts.

8 to 8.5- Very entertaining. Compelling story and characters. Worth watching.

7 to 7.5- Entertaining, but not memorable.

6 to 6.5- Barely watchable.

Under 6- Regret watching. Probably dropped.