Close drapes on south-facing windows before the suns begins to hit them. Any kind of covering will help, but some are made specifically to boost the effect, such as Levolor’s Energy Shield models (blinds shown above are from Levolor). Awnings can help too. The Sunbrella site cites a study by the American Society of Heating and Air Conditioning Engineers that says an awning can reduce heat gain by 55 to 65 per cent on southern-facing windows and 72 to 77 per cent on western exposures.
I love ceiling fans, and have one in almost every room. They help immensely, either by creating a breeze or, on the few times when I do turn the AC on, allowing me to keep it at sane setting.
A reader suggested putting in a pergola, or "celestory doors" to fasten onto the house to create an entry to a green and shady garden. Don’t forget that a tall shade tree on the south-facing side will help.
If you do install central AC, position the unit on a north wall and plant a shrub no less than 24 inches from the unit. That can save up to 10 per cent on your energy bill. (Just don’t let shrubs or weeds grow up around the unit.)
A well-insulated attic will keep your house cooler, so consider adding extra before it gets super hot. I recently used Owens Corning blow-in insulation with an AttiCat machine rented from Home Depot. Super-easy and WAY faster than I expected.
Lastly, why not just enjoy the heat? After all, it will be December before you know it!