hotest it got here in Melb last year was 46C and multiple days above 43C with extreme fire weather ~ http://www.flickr.com/photos/bootload/sets/72157614397725714... Couple of measures you take:
- open windows
- multiple 4Ltr freezer blocks work well
- stay at the pool till late
- sleep on concrete or tiles
- use fans
- wet towels & buckets of water for feet are pretty good
That and eat lots of icy poles (don't laugh) and drink water.
It really depends. On the really hot days having a window open increases the interior temperature if the previous days have been cooler. On successively hot days leaving the window open decreases the interior temp but only if there is a wind.
I don't know what latitude where you come from since you don't have any identifying information but being smart has nothing to do with understanding how to keep cool. It comes from local knowledge. If you come from the continental Europe or the UK I'd guarantee you'd miss half these hacks due to the heat.