Aquascaping

I'm about to move my 40 gal reef (Fri) to set it on a new stand. As long as
I'll have almost everything removed, I wonder if anyone has any good
guidelines on aquascaping. I know that all should "firm" so things don't
tumble (like they do now). I want to maximize the number of corals I can
place in the tank (it's sad when you run out of room). I know to leave nooks
and crannies for creature hiding places and water circulation and to leave
room to be able to clean the glass.

I have seen many tanks with a high center area and little on the sides, and
others with a level platform all across. Is there any advantage to either of
these setups? Which will allow more coral placements? Is sloping from the
rear to the front wise?

Any suggestions will be welcomed.

Steve