Sign up to a green energy supplier, who will supply electricity from renewable sources (e.g. wind and hydroelectric power) - this will reduce your carbon footprint contribution from electricity to zero
Turn it off when not in use (lights, television, DVD player, Hi Fi, computer etc. etc. ...)
Turn down the central heating slightly (try just 1 to 2 degrees C)
Turn down the water heating setting (just 2 degrees will make a significant saving)
Check the central heating timer setting - remember there is no point heating the house after you have left for work
Fill your dish washer and washing machine with a full load - this will save you water, electricity, and washing powder
Fill the kettle with only as much water as you need
Unplug your mobile phone as soon as it has finished charging
Defrost your fridge/freezer regularly
Do your weekly shopping in a single trip
Hang out the washing to dry rather than tumble drying it
Go for a run rather than drive to the gym