Ideally building properly. Having the windows in the right place and having good geometry to shade during the hot season. Having thermal mass inside of the insulation layer helps, having a roof that is not dark colored, having a good ventilated space under the roof is also effective. The most effective is to have the structure surrounded with earth.
But most the time one cannot start from scratch. So most economical and ecological to plant
trees for shade in the summer. This can take a while to feel the effect though. :/
Ventilation can help, if done right, but this also needs a structure with some mass.
Ventilation through a pipe that goes
underground, is a good solution. Needs to be properly sized for the home, so it can remain effective through the summer. Best combined with some structural changes, because having less need for cooling is better than having more cooling power.