Use cold water when washing clothes.
The hot water cycle of most washing machines uses 90% more energy per load than the cold water cycle. Using the hot water cycle can also shorten the life of your clothes.
Size does matter. Make sure you set the load size for your laundry to the correct setting and only wash full loads of clothes. Don't waste water and electricity on a half-empty washing machine.
Dryer:
Clean you dryer's lint filter with every load of laundry.
A clogged lint filter obstructs airflow and is a potential fire hazard. If you have to dry a load a second time, you use twice the energy and you double the cost.
Check the exhaust.
An obstructed exhaust vent can considerably lengthen drying times and cost you money.
Hang them up!
Whenever possible, hang your clothes to dry. Why? The sun's energy is free.