No, it's not your imagination—it definitely is getting hotter. The eight warmest years on record occurred over the past decade. But staying cool this summer doesn't necessarily mean you have to pay a fortune to keep the air-conditioning running day and night. Here are 10 tips—most costing less than $25—that will keep you comfortable and cut the typical $1,000 cooling bill by as much as half. What's needed to get the temperature to drop? Only a little time and a few changes in your routine.