when it comes to writing songs, i've always taken the whole write what you feel approach, however usually i end up with a load of crap on a page and a good idea, like u spill out your mind and there's a lot of mental/verbal/emotional diahroeah and then you hit somethin that is kinda awesome, and then you explore that emotion, or that topic/issue more and focus on that. Sometimes it helps to think of a central theme for a song and then write the chorus first if you're on a deadline or something, and then fill the rest in, but writing on a deadline, although it sometimes works, it mostly doesn't.