Stay indoors as much as possible. If air conditioning is not available, stay on the lowest floor, out of the sunshine. Wear lightweight, light-colored clothing to reflect away some of the sun's energy. Drink plenty of water regularly and often. Drink plenty of fluids even if you do not feel thirsty.
Water is the safest liquid to drink during heat emergencies.
Avoid drinks with alcohol or caffeine in them. They can make you feel good briefly, but make the heat's effects on your body worse. This is especially true about beer, which actually dehydrates the body. Eat small meals and eat more often. Avoid foods that are high in protein, which increase metabolic heat.