Electricity waste is a hit topic right now: There are so many "energy vampires" in our homes that waste electricity that we do not need to be using. This is detrimental to the planet, and costs money we don't need to be spending.
One of the biggest culprits is leaving devices on standby when not in use- particularly devices with an LCD display, like a microwave. If you think about how often a microwave is used, and there are probably some days when it is not used at all- it makes no sense to leave it on for all the rest of the time.
Other devices that waste energy are internet modems. These devices may be in use a lot when there are people in the house, but when everyone is out they continue to transmit signals which uses energy.
Finally, heating can also be a waste of electricity. Of course it is essential when it's the middle of winter, but be careful about putting your heating on a timer to come on at different times of the day, and then going on holiday for a week!