it's hard. I still have to remind my sons to turn off lights when they are not in a room :-(

Ditto. I am constantly walking through the house turning off computers, Playstations, and lights. I try and try to explain why we shouldn't waste energy. I have found that it is difficult to instill conservation in children.

Ditto,

Came into the computer room to find the kids had left the computer on all night. They absolutely don't get it.

I explained to my children and explain to my grandchildren that electricity and gasoline cost money. Kids as young as four or five can get the idea that the more money that is spent on electricity the less there is to spend on getting them stuff that they need or want. Sometimes it is hard to do this in a very gentle way, but patience pays.

A child who is wasteful at age five is likely to be a wastrel at age fifty-five. And definitely, if not by eight, then too late.

My own parents drilled a fanatical frugality into me from as early an age as I can remember--about three. I think one reason my wife left me was because of my strict habits of conservation and thrift.

BTW, it is tough to avoid a "holier than though" attitude as a stingy old man; I find that firmness, gentleness, and good humor help.

My seven year old gets on my case when I leave a light on because it hurts the earth.

If you have a toddler it's easy. Starting at age 2&1/2, I started carrying my daughter around the house to turn off lights at bedtime, or when we left a room. She gets it.

Put stickers on the switches when you do that.  Having to remove a sticker to turn something on will be a reminder.

Maybe put a Kill-a-watt on the offending devices and charge for energy?