trouble figuring out subjects in Japanese

I'm having trouble figuring out which is the subject in a Japanese sentence.  I guess I'm still not skilled enough to take it from context.  (lolwut?)  But say, in a song, does the subject stay the same throughout one verse if it's not otherwise stated?

This kind of learning will never work. Just my two cents.

wtf r u talking about?
u'll never learn japanese like that loser

before が

lrn2jpn