If you stop buying products that contain powerful greenhouse gases (high GWP gases), you can reduce your impact and you'll be doing something smart for the environment. You can do this by simply not using or using less air conditioning (in the car, at home or work), refrigerators (if you have more than one), foam products (styrofoam cups/containers, foam packaging, foam based home insulation, etc.) and aerosols (hairspray, shaving cream, etc.)
Buying smart also means buying used! Used items not only do you not add any new emissions caused by transporting manufactured goods from the point of production, you also stop the emissions that would have been caused by the manufacturing and packaging of this newly made item.