Possibly the most useful - and least understood - step we could take is to reduce our overall energy demand.
This doesn't have to mean a drop in our living standards - wastefulness is built right into the system we use. Many of our power plants (whatever the fuel type) waste around two-thirds of the energy that goes into them; our homes and offices are poorly insulated; our appliances keep using energy even on standby; our cars use only a fraction of the energy in petrol and diesel... the list is goes on.