What can families do to reduce carbon footprints on the earth?

It all depends on where on the globe you live, but since it all boils down to energy consumption, preservation and efficiency, the greater onus lies on people in the highly developed and industrialized countries. In this regard, emissions from private vehicles are the number one polluters, so they will need to cut down on use of these in favour of public transport, cycling or walking where possible. They will also need to cut down on energy consuming gadgets in their houses and last but not least cultivate trees and plants which can soak up some of the atmospheric carbon dioxide.