Think big? Well, we could make our energy use a lot cleaner by putting in a windmill (if the borough would allow it - I dunno - this could be a key obstacle) and/or with solar panels. I have looked into solar panels, though, and I'm told that our house is too shady (another key obstacle? I don't think we want to cut down all the trees.)
But even so, since we live in such a suburban location, we use motor vehicles a lot - to get to school or work, to buy groceries, etc (another key obstacle). I'm thinking that maybe when the kids are out of the house we might move to an apartment or condominium in a small city. There are a couple of towns not far from here that could fill the bill - we could walk to almost everything: shops, train station, library. Yeah, that about does it!
One thing that I always do, and will continue to do, is to use free heating and cooling as much as possible. That is, if the air outside is a more comfortable temperature than the air inside is (rare in winter, but frequent in spring, summer, and fall), I throw open all the windows. As soon as the situation reverses, I close the windows again.
An important thing that we could do this year would be to put in energy-efficient replacement windows. We might do that this summer.