Where to stay in Seoul? I'm always choose my accommodation in Seoul base on 4 main conditions:
i) Near Airport Bus station
ii) Near Subway
iii) Must have internet or WIFI
iv) Bathroom attach
Below are all places I have personally stayed and some feedback.

Important!
This is using in Seoul.
So please ensure you bring the correct adoptor if you wish to use your laptop, camera and mobile charger or other electronic devices in Korea. ^ ^