I don't often check out groups that are debuting not even when 2NE1 (aka my Queens) debut did I check them out it wasn't until they did Lollipop with Big Bang did I look into their own music.
I've gotten a little better at it because I checked Miss A, G.NA, F(X) along with more recent
The singer to really make me go "Geez, I really should have paid more attention to --- during their debut..." was IU, she was a guest on Running Man where she woke up the members by singing her song "Good Day" outside of their housing. The song was refreshing and I enjoyed her vocals, I caught my self humming the tune during the rest of the day, so I checked out quite a bit more of her songs You and I, Cruel Fairytale (my favorite!), and Lost Child.
Another artist I didn't follow from debut just made a comeback and that singer is NS Yoon Ji.
Some of my favorite debuts thus far are B.A.P, SPICA, and Fat Cat.
Another group I've had my eye on but hasn't debuted yet is SM's EXO
I'm biased, I love Tao!ㅋㅋㅋ