This is part of my answer to those boycott the oil companies chain letters that used to go around. Works for pollution, too...
From easiest, to hardest.
1. Don't idol needlessly: In the drive-through; waiting to pick up or drop off someone; leaving the kids in the car to watch a DVD while you run inside. If it's more than 30 seconds, turn it off.
2. Don't drive aggressively. If the light ahead is red, coast up there, no need to have one peddle on the floor at all times. In rush hour, you don't have to be right on someone rear, it wastes your gas and causes the domino effect of "stop and go traffic". Accelerate more slowly, you don't save much time and
it's a huge waste. Leave two minutes early so you don't have to drive like an idiot, a minute or two is about all you save.
3. Open the windows, turn off the air. This is especially for those of you who wait for someone or something while idling with the air on. Roll down the windows, you'll live.
4. Walk, bike, bus, train wherever and whenever you can.
5. Don't buy SUV's or other gas guzzlers. How many times do you pack it to capacity and use all that space. How much would you save on payments, gas, insurance, etc., if you bought a smaller car and rented a van/truck when needed. Buy a hybrid or a smaller car.
6. Live near your work. Work near your home.