The first step is to flush all the air out of your house (don't worry, we'll bring it back soon) and replace it with cooler air. This can be done with some open windows and well-positioned fans set up to push all the warm, armpity air out of your home as you sleep, replacing it with cool nighttime air. Then, around 4 a.m. or whenever it starts to heat up outside, you simply close all the windows, kicking your armpit air outside forever.
And possibly experience an odd sibling of empty nest syndrome.
Once the inside of your house is nice and cool, you can now turn to doing war with the sun itself. Anything you can do to stop sunlight from shining into your house, like closing drapes or blinds, will stop that radiation from getting inside and heating up your shit. Even better is to keep the sun from touching your house and heating up its shit. By planting big leafy trees on the southern exposure, installing external shades, or putting your house on wheels and driving around the country following the clouds, you'll prevent a tremendous amount of energy from ever reaching you in the first place.
Some of these tips are a bit less economical than others, I guess.