The answer is to keep the listener engaged.

It's like asking where a chorus should be placed. There's the old cliche "Don't bore us, get to the chorus", but one song might need more development before bringing in the chorus, while another song might start with the chorus.

Mario mentions "hooks", and it's the same idea - what are you doing in the song to keep them engaged and wanting to continue to listen? A provocative line opening a verse gets a users attention; a developing story keeps their interest; a satisfying chorus brings everything together; development in additional verses gives new meaning to the chorus...

I can recognize when it's done right in a song.

But it's not so easy to do it myself, though. cry

-- David Cuny
My virtual singer development blog

Vocal control, you say. Never heard of it. Is that some kind of ProTools thing?