Re: how dj'ing relates to song structure..?
Sometimes, I sit myself down and either a) Copy a tune as good as I can, regarding beats, bass, melodies and such, or - b) Sit myself down and write just a very simple tune with sort of "template"-parts and finish it. Both aren't nescessarily grand and epic works in music, but whenever I have done this, I have always learned a lot for my next tracks.
I guess you can call it.. Training? Sort of. All I know is that it's worked for me. That, and listening to really, really, really much music from different genres. Everything from pop songs, rock, funk and to dubstep, drum and bass and the likes.. As well as everything inbetween. The more you know, the more you can do.
Oh, and fuck templates as soon as you're done with them. There is nothing in the world that can hinder you creatively than rules in music. I've never done 64 bars of anything to an intro - less, probably more, but, honestly, I don't think I've ever done 64. And it doesn't make my music suck. Usually it does quite the opposite, and it'll be more interesting to other people as well.