Simple changes around your house will save you money. Some of the changes I have mentioned in the past include things easy to do in a finished house like:
Those are all fairly easy to do in an existing house. However, if you are doing a bigger renovation or changing out flooring you can caulk the wall to the subfloor. This is a huge air leak in most of the houses that I do audits on in the area. Adding caulk around the inside and outside walls will limit air leakage and reduce your monthly energy bills.