Exhausts should be as far to the rear and as far to the top of the case as possible. Power supply should be mounted with the fan facing downward (into the case, actually, there will be a little slot for it to still draw air so don't worry). Side fans should blow onto the graphics card and/or CPU cooler and the fans at the front should be intakes to facilitate the flow of air in a single direction. Remember that a lot of fans mean a lot of dust - and I really do mean A LOT. Consider fan filters, and if that isn't available you can use normal pantyhose, doubled up and screwed tight under the intake fans (no need for filters on the exhaust fans, obviously). It's cheap and effective, and once they get too dirty you simply replace the pantyhose as a whole.