You might find Karpov's new book, Find the Right Plan, (2010), useful.
He describes a variety of pawn formations in the opening, and talks about how to form a plan for the middlegame. It's a bit deep, but I believe he is (effectively) answering the type of question you pose above.
As you well know, there is no simple answer, or rule of thumb to pursue. Karpov breaks down the question of where to attack (or expand) into about 6 categories.
The basic theme of the book is -- "Restrict the Mobility of your Opponent's Pieces." Often times, that's much easier said than done.
As black and white I've always played more for flank games, hypermodernism and the like. Recently I've taken a more active role in controlling the centre as I've switched to e4 but find that I'm always on the defensive foot, trying to hold my strong centre against black's attacks. My question is once you hold the centre, what's your strategy? Surely at some point you have to flip to attacking the king or queenside? If so when? Also, I've noticed that a massively strong pawn formation isn't required to control the centre. Pawn exchanges can result in white having an isolated pawn on e5 which still limits black's play but don't you end up being on the defensive foot all the time, trying to hang on to a weak pawn?
Thanks for any advice! :-)