ACTORS?

POPULARITY OF THE DRAMA?

SYNOPSIS? 

OTHERS. 

The first thing for me is the ACTORS.  2nd is the theme.   3rd. The length. 
Theme
Actors
Idols
Length
Synopsis 
Quality
Actors
Length
1. synopsis
2. combination of promotional images and actors to see if I think I can take them in their role seriously
3. trailer
4. combination of hype on forums and tv ratings
5. length
Actors
Theme
Length
Quality
Genre, Theme
Actors
Length
Music

Popularity? Maybe only a tiny little bit~
My basis for watching a drama are these factors:

1. Actors
2. Genre
3. Storyline
usually I'm into a certain theme and watch a couple of similar dramas or I'm into a certain actress/actor and watch a couple of dramas from her/him. If I haven't watched dramas in a while, I usually look more at the plot/something new 
The first thing I consider is the plot followed by the actors. Even if there are actors/actresses that I like in the drama, if the plot is not interesting for me, then I won't watch it. Though there are some cases when I tolerate the plot just because of the actor/s that I like. Then, the length. As I generally prefer Jdramas, this is an issue to me.
First, the story, second the good acting.
Plot
Actors
Reviews
First four episodes (I like to give them four.... its the nice thing to do)