Drinking Gatorade is my first preventive, aside from taking a potassium tablet every morning. I refused to drink Gatorade for years, simply because I couldn't see paying the price they wanted for it at convenience stores. Then in '05, the week after Katrina hit, I hired a guy who graduated with my brother who was just out of college and looking for something temporary. (Roofing didn't please him well.) The first day on the job, he offered me a Gatorade and I accepted. I could tell the difference that afternoon from drinking that one Gatorade. I picked up a can of the powder from Walmart that weekend and have been carrying it to work with me ever since whenever it's hot. I can mix it for under 25 cents a quart. My little cooler holds 6 12-oz bottles just perfectly.
I used to cramp every day before I started taking the potassium tablets and drinking Gatorade. Forearms, shoulders, back, calves, thighs, you name it, it cramped. The absolute worst is the belly. I've had them that felt like a golf ball in my belly. And unlike other muscles, where you can stretch the cramp out, you can't bend back far enough to get an abdominal cramp out. I've come home from a hot day at work and sat down to supper, opened my mouth to take a big bite of something, and my jaw/neck/throat/whatever-it is-that-opens-your-mouth would cramp so bad I couldn't chew my food. Since the potassium and Gatorade, I don't cramp near as bad, and I've been thinking of taking a magnesium supplement as well.
I've heard and read that too much Gatorade can cause kidney stones, so I make sure to drink at least 3 bottles of water to every bottle of Gatorade. I often drink over 2 gallons of water a day when it's hot.
water --- but everyone is different 
