If this hasn't already been suggested, here's a tip: run the cold water tap until it's really cold, then put your wrists under the water. Your whole wrist, the vein side. What you're after is to cool the blood as it flows through. Great way to ease a headache, but cools down the body a bit too. Cold flannel or something on the back of your neck too; same idea. Mainly, the wrist thing. Also, avoid straining yourself. Drink cold liquids. That's all I can think of, I'm afraid.