Use your compass to find a spot that will be shaded during the hottest part of the day, from late morning to late afternoon. When you're camping in the heat, lots of shade will make the single biggest difference in keeping you comfortable.
Wear cool, loose-fitting clothing around your campsite. Tight-fitting clothing will make you feel hotter.
Drink plenty of water to stay hydrated throughout the day.
Leave your campsite during the hottest part of the day and do something that cools you off. Swimming and wading in a nearby lake or stream will make you feel cooler even once you return to your site.
Make up your bed with a sheet, and avoid hot, stuffy sleeping bags. Have a light blanket handy in case the temperature drops significantly during the night.
Set up a battery-powered fan in your tent so it blows the night air in through a window to keep air circulating. Lay very still and let the breeze cool you down until you are comfortable enough to sleep.
