From a Design standpoint, it goes without saying to spend the extra money for the energy efficient appliances. An option that is not as difficult to do these days, but still needs to be thoughtfully considered.
There are some simple changes from a lighting Modern Bathroom Lighting Guys by changing out some of the bulbs that are claiming to be more efficient. I am not talking about going crazy and just start changing them out, but when you need to make a change, do so then.
Also look at you filters in heating and air conditioning units. My Dad was a heating and air guy for years and was always shocked as to how people just wouldn't take the time to change the filters which would cause countless dollars in repair bills yearly. There are some pretty decent filtration systems, but are still a little pricey compared to regular ole filters.
Finally, from a Kitchen Design standpoint, Bamboo and cork flooring should be considered in Interior Design, as they are dynamic looking. Kitchen cabinets can also be redone with similar alternatives to wood which can like just like exotic woods.