For short trips consider riding your bicycle or walking. Other options include carpooling, vanpooling, working at home, faxing, teleconferencing. Ride the bus. Capital Metro provides free rides on all its buses on Ozone Action Days. Minimize cold starts by combining trips.
Most vehicle emissions occur when the engine is cold.
Avoid traffic congestion. Don't idle your engine. Avoid lines at drive-through windows. Delay buying gasoline until the evening when it's cooler. Avoid spilling gasoline and don't top off the tank.