My wife and I are renting a small home in South Africa while she does her Ph.D project in a nearby nature reserve. Wanting to eventually start a permaculture farm, I looked at our current situation and asked "what can I do right now to make a difference?" What I found was the outdoor hot water heater and pipes were not insulated. In the winter it can drop below freezing in the night, so we asked the landladies if they could supply the insulation. They came up with old, used insulation that had been stored for a few years in a chicken coop. I thought this was perfect- reusing instead of buying new. It did mean that there was a lot of custom fitting to be done, it does not look very 'professional' (I have insulated pipes on oil rigs which had to be held to a different standard) but I couldn't be any happier. We have also committed to buying local farmers' eggs and fruit from trees in season, but there are no local vegetable producers unfortunately.
Am on the lookout for whatever other changes we can do, the sum of the infinitesimal equals real change.