1. Conserve energy. Don't blast the AC at home or the office. When you drive, keep your tires inflated, combine trips, don't accelerate rapidly, and don't speed. If possible, carpool, take public transportation, or even walk/bike. Replace incandescent light bulbs with more efficient bulbs (CFL, LED, etc.) and turn them off when you're not using them.
If you can afford it, there are other ways you can save energy (and, over time, money). Buy energy efficient appliances. Buy a hybrid. Insulate your home. Buy insulating windows.
2. Go green. If you can *really* afford it, look into solar panels and geothermal energy.
3. Raise awareness. Get informed on the issue of climate change. Contact your representatives and let them know this is important to you. And don't forget to vote.