Water

The biggest user of water in the home (30%) is from flushing the toilet.  Make sure you have a low flush toilet, that is 4.5 litres or under.  If you can't afford a low energy flush toilet then place a "hippo" bag (available from the water board) in the cistern.  Better still, fill a plastic milk container with water and place that in the cistern.

You can also recycle your "grey water", that's the water from your bath, dishwasher, shower, washing machine, etc.  This makes up almost half of all residential waste water and can be useed for watering the garden and washing the car for example.