Turn off lights you're not using
This is a simple one you likely already know. Simply turn off lights when you leave a room or do not need them. It saves electricity, reduces pollution from energy generation, and lowers your expenses. There are extra bonuses as well. It extends the life of your bulbs so you buy new ones less often.
Some say that if you’re going to need the light again within a short amount of time (say, 5 or 10 minutes), it takes less energy to leave it switched on. This is wrong:- across all common domestic bulbs (LEDs, CFLs, halogen, etc), even if you’re going out of the room for a few seconds, it’s worth getting into the habit of switching off that light!