Open all of your windows at night. Run fans facing inward on one side of the house only, so the breeze runs through the house. Close the windows in the early morning when the temperature is coolest and keep them closed all day.
Avoid cooking and other heat producing activities during the hot part of the day.
Live in a neighborhood with lots of shade trees.
Have a house that was built before ac was ubiquitous.
Have your bedroom on the main floor or basement if possible.
High ceilings!
I'll second window fans. We have a pair of these in bedroom windows. We open only the windows in the family room. The air comes through the family room and exits the bedroom windows while we are awake.
Once we go to bed we reverse the flow of the fans and the air enters the bedrooms and exits the family room windows. Side benefit: the house smells so fresh.
These window fans (in case you haven't seen them before) are rectangular and are designed to have the window closed on them to loosely seal the window and allow the air to only go through the fan. Some come with thermostats so they can be set to cycle based on interior temps. Our fan thermostats never worked b/c there wasn't enough temp change as found in the desert perhaps. The air flow provided the comfort.
Daytime comfort: shady screened in porch. Alternative: a portable pop-up canopy with screened walls plus a portable fan.
I live in a hot and humid place. Being comfortable can be a dozen little strategies.
Clothing: look for something thin. I'm wearing a athletics type polo shirt that is prob mostly synthetic material. Very breezy. Some of my cotton t-shirts are thinner than others and thus cooler.Take up wearing women's clothing for the summer. I'm guessing a women's skirt made of light fabric might beat men's shorts for making the most of a breeze. ;)
Drink COLD ice water frequently.
Don't sit on upholstered furniture. Our family room furniture is very comfortable but very warm (foam padding and upholstery). Sit on the floor, wicker furniture, camp chairs, etc.
Heat sources: Summer kitchens. People I've known in hot places that cooked alot (esp. simmering) did so on a second stove/range on an outside porch to keep the heat out of the house.
Heat sources: stereos, televisions, and incandescent light bulbs. Turn them off or minimize their use. LED bulbs win here. So do laptops vs televisions. Desktop computers make alot of heat even at idle.
Sleeping: Siesta. Take one. Be active in the cool early and late hours of the day. Sleep outside on a screened in porch.
Entertainment: Go see a movie during the hottest part of the day. Reserve your shopping for the hottest part of the day. Visit the library. All these places are air conditioned.
Wear a hat. A straw hat can be cooler than others. A wet fabric hat can be cooling too.