In a drama, I personally value these things in this order:
Story/Script
Characters/Character Development
Acting/Actor Chemistry
Visual Effect Quality (CGI if applicable)
Action Choreography
OST Music/Music Timing
Actor Attractiveness
Thus, my ratings are loosely weighted in the same way. I only rate dramas that I finish.
Specific aspects of dramas I like the most that don't necessarily affect my ratings:
Mature, realistic romance
Romance is present, but not made as important as the plot
Well designed/executed fight choreography
Multifaceted characters (especially villains)
Fleshed out side characters
If you like some of the same things, then maybe my list will be useful to you.
Actors/Male singers I like a lot: Lee Joon Gi, Liu Yu Ning, Li Xian, Alen Fang, Liu Xue Yi, Bai Jing Ting, Liu Yi Jun, Zhou Shen, Lars Huang, Jonghyun, Hou Ming Hao
Actresses/ Female singers I like a lot: Shin Hye Sun, Julia Xiang, Bai Lu, Zhao Jin Mai, Song Zu Er, Liu Shi Shi, Lu Yu Xiao, Zhao Lu Si, Wang Chu Ran, Liang Jie, Xing Fei, He Lan Dou, Dai Lu Wa, Tian Xi Wei, Zhou Ye, Jane Zhang, Zhang Bi Chen, Shan Yi Chun, Ailee, Hyolyn, Lee Hi, Wendy, Si Yeon, Deng En Xi, Wang Yu Wen, Kim Hye Yoon