Here is a relatively simple time for saving some money:
Wash full loads of laundry.
The machine uses the same amount of energy no matter the size of the load, although you can adjust the water lever, the power used does not change.
Do not stuff the machine full, as this causes the clothes to not be able to move freely to get clean. Make sure that you use the water setting so that there is enough water to cover the clothes in the machine. A front load machine uses less water than a top load, so if you are in the market and can afford one, your better option would be to go with a front loader.