Do you live with people who leave the lights on in practically every room?
Sure, you can remind them to turn off the lights when they leave the room. I read about a “Lights Off Fund” somewhere while surfing the net. Every time someone at home forgets to turn off the lights, they have to donate money to the fund.
Another good solution? Use occupancy sensors. No one has to be the Lights Patrol. The sensors will do the job easily.
Better yet, use the money from the “Lights Off Fund” to buy occupancy sensors. Give it a try.